
Book. '-■ 

COPYRIGHT DEPOSE 



APPLIED CHEMISTRY 



APPLIED CHEMISTRY 



AN ELEMENTARY TEXT BOOK 
FOR SECONDARY SCHOOLS 



BY 



FREDUS N. PETERS, PH.D. 

Instructor in Chemistry in Central High School, Kansas City, Mo., for 

twenty-three years; More Recently Vice-Principal; Author 

of "Chemistry for Nurses," etc. 



ILLUSTRATED 



ST LOUIS 

C. V. MOSBY COMPANY 

1922 









Copyright, 1922, by The C. V. Mosby Companv. 
(All rights reserved) 



Printed in U. S. A. 



**1 20 i922 



Press of 

C. V. Mosby Company 

St. Louis 



■CU674225 



C,To the hundreds of young men 
and women, students of mine in the 
past, whom it has been my privilege 
to know and to love ; especially to 
my own son, Fredus Nelson, Junior, 
who in his early childhood, playing 
at chemistry among the bottles and 
apparatus of my laboratory, found his 
chief delight and who now in his 
early manhood gives promise of at- 
taining to heights in this realm of 
science of which his father only 
dreamed, this little book is affection- 
ately dedicated by the author. 



PREFACE 

The author is not very sure but that the preface of any 
book is a useless page. It is doubtful whether a sufficient 
number ever read this personal letter of the author to 
pay him for the writing or the publisher for printing it. 
Yet every writer by force of custom feels compelled to 
address his readers by a foreword. 

Like Livy, in his preface to his History of the Roman 
People, I do not know whether I am doing a work worth 
while in putting another text of elementary chemistry be- 
fore the public ; and even if I knew, modesty would forbid 
that I speak very strongly. 

Permit me to say that to me it has never seemed neces- 
sary for a high school chemistry to present a mere skeleton 
of the most interesting of sciences when that skeleton may 
just as easily be clothed with wonderful symmetry and 
charming beauty. On the contrary, it has always seemed 
that a text for secondary schools may and ought to be a 
readable book just as well as one merely surfeited with 
facts. No dinner menu is complete which offers nothing 
but lean meat and vegetables. It may thus contain all that 
is essential, but far from all that is desired. Entrees and 
desserts round out the repast and give a sense of satisfac- 
tion not otherwise possible. 

Such is the attempt of this text, to present the chemical 
facts of every-day life in a readable form and by so doing 
make them interesting. If this cannot be done, for most 
students the book is a failure. 

To the teacher let me say that my long experience com- 
pels me to believe that very few classes, in a school year of 
nine or ten months, are able to complete a text of this size. 

11 



12 PREFACE 

Some portions must be omitted. No one in a table d'hote 
dinner is expected to order everything on the bill of fare. 
Let him use judgment and discretion, the teacher likewise. 
Almost a quarter of a century has elapsed since I began 
my work in Central High School in Kansas City, one of 
the great high schools of the Middle West. I should not be 
true to my own better self did I fail to acknowledge my 
debt of gratitude to the hundreds of students whom I have 
had in that time. In this particular work I wish to thank 
especially Mr. J. U. Young, now head of the department 
of Chemistry of Central High School, Kansas City, for his 
many valuable suggestions and also Mr. G-. W. Davis, of 
the Northeast High School, Kansas City. I am also under 
obligations to Mr. G. H. \Vilkinson of the Physics Depart- 
ment of Jefferson High School, Los Angeles, Cal., who has 
been of material assistance in reading the manuscript ; to 
Mr. F. N. Peters. Jr.. of the Department of Chemistry of 
the University of Missouri, for suggestions in methods of 
presentation of certain gas laws, to Mr. V. W. Peters, of 
Los Angeles. Cal., for drawings from which many of the 
illustrations were made ; to the Goldschmidt Thermit Co., 
of New York City, for illustrations of thermit welding, to 
the Permutit \Yater Softener Co., of New York, as well as 
to two or three publishing houses who have extended 
courtesies in the way of illustrations. 

F. N. P. 

Los Augeles, California. 



CONTENTS 



CHAPTEK I 
A Study of Matter 21 

CHAPTEE II 
Water and Hydrogen Peroxide .......... 34 

CHAPTEK III 
Oxygen and Ozone 51 

CHAPTEK IV 
Hydrogen 63 

CHAPTER V 
The Atmosphere . 72 

CHAPTER VI 

Gases and Some Gas Laws 84 

CHAPTER VII 

Symbols and Formulas , . . ... 106 

CHAPTER VIII 
Some Chemical Problems 112 

CHAPTER IX 
The Halogens 119 

CHAPTER X 
Acids and Bases 136 

CHAPTER XI 

Nitrogen and Compounds 145 

13 



14 CONTENTS 

CHAPTER XII 
Carbon 159 

CHAPTER XIII 
Valence 178 

CHAPTER XIV 
Illuminating and Fuel Gases 183 

CHAPTER XV 
Flame 189 

CHAPTER XVI 
Methods of Lighting 197 

CHAPTER XVII 
Some Organic Compounds 203 

CHAPTER XVIII 

Ethereal Salts, Oils, Fats, Sugars 212 

CHAPTER XIX 
Foods and Their Body Values 224 

CHAPTER XX 
Solution and Ionization 233 

CHAPTER XXI 
Sulphur and Compounds 249 

CHAPTER XXII 
Periodic Classification of Elements . ^ 265 

CHAPTER XXIII. 
The Nitrogen Family 274 



CONTENTS 15 

CHAPTER XXIV 
Compounds of Silicon . . 294 

CHAPTER XXV 
The Alkali Metals 305 

CHAPTER XXVI 
Some Leavening Agents 327 

CHAPTER XXVII 
The Calcium Family 336 

CHAPTER XXVIII 
Hard Waters — Methods of Softening 316 

CHAPTER XXIX 
Cleaning and Polishing 353 

CHAPTER XXX 
The Copper Group 362 

CHAPTER XXXI 

The Magnesium Family 379 

CHAPTER XXXII 
The Aluminum Family 392 

CHAPTER XXXIII 
The Lead Family . 402 

CHAPTER XXXIV 
The Chromium Family 411 

CHAPTER XXXV 
Manganese and Compounds 416 



16 CONTENTS 

CHAPTER XXXVI 
The Iron Group , . . 419 

CHAPTER XXXVII 
Tee Platinum and Palladium Groups 434 

REFERENCE TABLES, AND GLOSSARY 
Reference Tables and Glossary 437 



ILLUSTRATIONS 

FIG. PAGE 

1. Abundance of certain elements 26 

2. Showing the "north" end of a magnetic needle being at- 

tracted by the * ' south ' ' end of another 28 

3. Wire showing the anode and the cathode 29 

4. Electrolysis or Hoffmann apparatus ........ 37 

5. Composition of water by weight 39 

6. Manometer used in testing gas pressure 42 

7. Diagrammatic view of city water plant ...... 4G 

8. Roosevelt Dam, which is very similar to the one at Sweet- 

water . 47 

9. Showing relative abundance of oxygen in nature ... 52 

10. Preparation of oxygen 53 

11. Preparing oxygen from sodium peroxide 54 

12. Boiling water in paper cup 57 

13. Machine for making ozone 59 

14. Electromotive series of metals and bar magnet with iron 

filings attached 65 

15. Preparing hydrogen from water by means of sodium . . 66 

16. Preparation of hydrogen from acids 67 

17. Oxyhydrogen blowpipe 68 

18. Lavoisier, beheaded in French Revolution, the Father 

of Modern Chemistry 70 

19. Nodules in which the nitrogen-fixing bacteria live on the 

roots of a bean 77 

20. Dewar bulbs. The thermos bottle is merely different in 

shape . . . . 81 

21. Comparison of thermometers 85 

22. Aneroid barometer 88 

23. Illustrating pressure of water vapor 91 

24. Contraction of volume on mixing two liquids .... 94 

25. Dalton, who proposed the atomic theory of matter . . . 98 

26. A simple eudiometer connected to induction coil . . . 101 

27. Preparation of chlorine in the laboratory 121 

28. Manufacture of chlorine 122 

29. Effect of sunlight on chlorine water 124 

I 17 



18 ILLUSTRATIONS 

FIG. PAGE 

30. Apparatus for purifying iodine by sublimation .... 132 

31. Method of determining approximately the proportion of 

nitrogen in the air 14(5 

32. Manufacture of ice 149 

33. Preparation of nitric ncid 152 

S4. Some forms of smokeless powder 156 

35. Burning of a diamond 1(51 

36. Moissan's electric furnace 162 

37. Oil derricks, a familiar sight in oil-producing sections . 165 

38. Formation of carbon monoxide in a furnace 169 

39. Pouring carbon dioxide upon burning candles in a trough 172 

40. Babcock fire extinguisher 174 

41. Acetylene burner 184 

42. " Burning" air 191 

43. Match suspended within burning gas jet 192 

44. Burning gas drawn from center of candle (lame .... 193 

45. Determination of flash point of an oil 198 

46. Starch granules 221 

47. Foods rich in iron 231 

48. Foods rich in phosphorus 232 

49. Ionization of a solution of common salt, and proof of same 242 

50. Method of obtaining sulphur in Louisiana 250 

51. Sulphur crystals 251 

52. Chamber process for sulphuric acid 261 

53. Manufacture of phosphorus . 276 

54. Preparation of phosphine 279 

55. Marsh's test for arsenic 283 

56. A scene in one of the petrified forests in Arizona . . . 295 

57. Mold for making glass tumblers 300 

58. Mold for blowing glass bottles 301 

59. Making window glass 302 

60. Preparation of sodium by the Castner process .... 307 

61. Preparation of salt in San Francisco Bay, by evaporation 

of sea w r ater 310 

62. Scale in iron pipes, from an actual case 347 

63. Making an electrotjpe 367 

64. Hydraulic mining 375 

65. Manufacture of aluminum 394 

66. Thermit crucible, sectional view 395 



ILLUSTRATIONS 19 

FIG. PAGE 

67. A thermit crucible ready for use in mending a broken 

casting 396 

68. A thermit crucible in operation, mending a. broken casting 397 

69. A battery " grid" 408 

70. A blast furnace for preparing cast iron 421 

71. A blast furnace, showing the molds for the "pigs" in the 

sand 423 

72. The Bessemer converter 425 



APPLIED CHEMISTRY 



CHAPTER I 

A STUDY OF MATTER 
Outline — 

Introduction 

Former Method of Reasoning 

Present Methods of Scientific Investigation 

Old Theories of Matter 

(a) Composition of 

(b) Transmutation 
Present Ideas 
Elements 

Compounds 

(a) Definition of 
(&) Chemical Union 

(c) Method of Naming 

(d) Explanation of Chemical Union 
Chemical Changes 

Kinds and Illustrations 
Mixtures 

1. Introduction. — Nearly every normal child is born 
an interrogation point. Almost as soon as he can form 
sentences be begins asking "why;" and many a Christ- 
mas toy has served best by its sacrifice upon the altar 
of childish investigation in the effort to learn what 
makes the noise, or why the wheels go around. The his- 
tory of the child is largely the history of the human race. 
Were the spirit of inquiry not crushed out in childhood, 
grown to youth and maturity, all would still find the 
greatest pleasure in studying the phenomena of nature. 
Some few survive the rebuffs and repressions of ehild- 

21 



22 APPLIED CHEMISTRY 

hood and to them nature ever speaks in loving and 
fascinating words. Others must have this instinct of 
investigation revived in their hearts if they find pleas- 
ure in any science. 

Chemistry as one branch of learning probably enters 
more largely into the affairs of ordinary everyday life 
than any other. "Without it, not only would most of the 
great engineering achievements of the world, such as 
the construction of great bridges and transcontinental 
railways, and the Panama Canal; not only would the au- 
tomobile and the airplane and all other modern means of 
rapid transportation be unknown, but the many little 
things of life would be mysterious and unintelligible. 
Cookery is a science dependent in many ways upon 
chemistry; pure foods and drinks can be kept so only 
by a knowledge of chemistry; healthful air and sani- 
tary conditions in the home must be secured by a knowl- 
edge of chemistry on the part of some one. Careful 
investigation shows that a knowledge of chemistry must 
be had for scientific progress in almost every line of 
human activity. This little book, therefore, will seek 
to be helpful in furnishing such chemical information 
as shall be needed in the affairs of the home and in 
giving added interest to everyday life ; such, that these 
affairs may be administered the more wisely and that 
nature may speak the more intelligibly; such that those 
who read may not only add to their own pleasures but 
contribute to the welfare and happiness of all who may 
come under their influence. 

2. Source of Scientific Knowledge. — There was a time 
in the world's history when scientific knowledge was 
thought possible of attainment by reasoning alone. Aris- 
totle, it is said, maintained that a vessel filled with ashes 
or sand would hold as much water as if there were no 



A STUDY OF MATTER 23 

ashes or sand in it. He never made the experiment to 
prove or disprove the truth of his statement and such 
was the strength of his influence, and such the method 
of reasoning* of the times and long after, that centuries 
passed before anyone sought to question by experiment 
the truth of his statement. 

3. Present Methods. — In this age of the world every 
statement of scientific fact or supposed fact is sub- 
mitted to the most rigid and searching examination; 
not only is reason applied, but every possible method 
of testing experimentally the truth of the statement is 
used. To illustrate: Some years ago one of England's 
greatest chemists announced in a paper read before a 
scientific gathering that he had succeeded in making a 
certain amount of lithium from copper by the use of 
radium. The next morning's sun had hardly risen be- 
fore many of his hearers were preparing to repeat his 
experiment, not for the sake of the experiment, but to 
prove or disprove his claims. So, in the present age of 
the world, every theory of every scientist, no matter 
how noted he may be, or however plausible his theory 
may seem, must be subjected to the test of practical ex- 
periment before it can be accepted as a scientific fact. 

4. Some Abandoned Theories. — As a result of the 
manner of thought of centuries ago, many theories were 
accepted as sufficiently plausible which long since have 
been abandoned. When a vessel of water is left exposed 
to the air or placed upon some source of heat, the water 
disappears. Centuries ago it was believed that water 
upon the addition of heat is changed into air; further, 
that the air upon the removal of the heat again be- 
comes water. This was based upon a very superficial 
observation, first the disappearance of the water as 
stated, and second, its appearance upon the surface of 



24 APPLIED CHEMISTRY 

any cold object brought into a warm room, as upon 
the outside of a tumbler of ice water. But no careful 
experiments were ever made to prove or disprove the 
theory. It was also believed that when water is boiled, 
a portion of it is converted into an earthy substance. 
True, upon the inside of the tea-kettle in the kitchen a 
hard, brittle crust gradually forms, but this is simply 
mineral matter which has been previously dissolved in 
the water. Pure water never leaves any such residue. 
But the old philosophers never made the experiment 
with pure water, as they might have done, to prove 
the truth of their position. 

5. Transmutation. — At the time chemistry had its 
birth, philosophers believed thoroughly in the possi- 
bility of the transmutation of one substance into an- 
other. Just as they maintained that water could be 
changed into earth and air, and air into water, so they 
believed one metal could be transmuted into another. 
They had observed some things that to them seemed 
sufficient evidence. Often, in their copper mines they 
had noticed that the iron tools left standing for some 
time in the water, which seeped in, became reddish in 
color and looked as if the iron were changing to cop- 
per. This may be seen by putting a bright nail or 
knife blade into a solution of blue vitriol for a minute 
or two. A deposit of copper really forms upon the 
iron, but it may be shown experimentally that the two 
meta^ are simply being exchanged for one another 
and that the iron is not changing into copper. They 
knew also a process for making brass by fusing copper 
with an ore of zinc which they called cadmeia. They 
recognized there were vast differences between brass and 
gold, yet never did they doubt that it was entirely pos- 



A STUDY OF MATTER 25 

sible to change iron into copper and this into gold ; in 
fact they strongly believed in the possibility of trans- 
muting any metal into any other if they could but 
learn the method. 

6. Matter. — Matter is anything which occupies space, 
and may be visible or otherwise. Thus, air is matter 
just as much as is water or wood or iron. What the 
real composition of matter is has long been one of the 
great questions of man. There have possibly always 
been those who believed that there is but one kind of 
matter in all the world, and that everything we know 
is simply a modified form of this one kind. On the 
basis of such a theory it was not hard to believe in 
the transmutation of the metals. Others claimed there 
were four primary substances, — earth, air, fire, and 
water, and that these in a way could be changed from 
the one into the other. 

7. Present Theory. — Robert Boyle, sometimes called 
the Father of Physics and Chemistry, who was born in 
1626, advanced the theory that there is a large number 
of kinds of matter, how many no one knows. To these 
primary forms he gave the name of elements, and the 
truth of his view has long been accepted by most of 
the scientific world. According to this idea, an ele- 
ment is a substance that cannot be divided into two or 
more kinds of matter. Thus gold is believed to contain 
only gold and copper nothing but copper. At present 
there are known 83 elements, the greater portion of 
which exist in comparatively small quantities, and 
most of which have been discovered since the beginning 
of the nineteenth century. Of these, eleven are gases. 
two are liquids, and the others solids. Some of the 
rarer may on more careful study be found not to be 
elements, while others as yet unknown Avill probably be 



26 APPLIED CHEMISTRY 

discovered. It is estimated that two elements, oxygen 
and silicon, constitute about 75 per cent of all the mat- 
ter of the earth and seven others nearly all the re- 
maining 25 per cent. Clark gives this table: 

Per cent 

Oxygen 49.98 

Silicon 25.30 

Aluminum 7.26 

Iron 5.0S 

Calcium 3.51 

Magnesium 2.50 

Sodium 2.28 

Potassium 2.23 

Hydrogen 0.94 

The same facts are shown more graphically in Fig. 1. 



Oxygen 50 % 


Silicon 25 Jo 


E 

3 
3 




JUKI 

s fcll 



Fig. 1. — Abundance of certain elements. 

8. Compounds. — A compound is a substance contain- 
ing two or more elements chemically united and in- 
variably in the same proportion by weight, The most 
familiar of all compounds is water, which consists of 
two elements, hydrogen and oxygen, always in the pro- 
portion of 1 to 8. Common salt is another compound 
containing the two elements, sodium and chlorine, al- 
ways united in the proportion approximately of 46 to 
71. 

9. Chemical Union Denned. — In defining a compound 
in the preceding paragraph the expression, chemically 
united, was used. If two substances are mixed, the re- 
sulting product will partake of the nature of each in- 
gredient. Two white substances will give a white pro- 
duct, a red and white will give a pink, a white and black 



A STUDY OF MATTER 27 

a gray. But if two substances differing from each other 
unite chemically the product formed may not partake of 
the properties of either even to the slightest extent, and 
will be essentially different. To illustrate : Hydrogen 
and oxygen are both colorless gases, the former inflam- 
mable ; the latter essential for life and ordinary combus- 
tion. When the two unite chemically, at ordinary tem- 
peratures, the resulting product is a liquid, which is not 
only not inflammable but will even extinguish fire and 
cannot be inhaled. Sodium, in common salt, is a soft 
metal, silvery white in color, which upon the moistened 
hand or in the mouth would catch fire and produce most 
serious burns. Chlorine, the other ingredient, is a heavy 
yellow gas, terribly destructive of life if inhaled and 
used with frightful results in the late great war. When 
these two unite chemically each loses its properties, and 
the two produce an entirely new substance, not only not 
harmful, in ordinary quantities, but even regarded as an 
essential in the animal economy. Likewise, two white 
substances, uniting chemically, may produce a brilliant 
red, as do potassium iodide and mercuric chloride; two 
gases may form a solid, as will ammonia and hydrogen 
chloride ; two liquids a solid. Many of these in great 
variety will be taken up from time to time and need 
not be emphasized here. 

10. General Plan of Naming Compounds. — A few gen- 
eral statements as to how compounds are named will be 
helpful at this time. In the early days of chemistry 
no plan was followed in naming the various substances 
prepared. As a result, peculiar and fantastic names of 
very familiar things have come doAvn to us. At the 
present time so vast is the number of compounds known 
- — hundreds of thousands — that some very definite and 
systematic method is necessary. In most cases as soon 



28 APPLIED CHEMISTRY 

as a chemist hears the name of a compound, he knows 
its composition even though it may be one not familiar to 
him. Common salt is chemically known as sodium chlo- 
ride, and one knows immediately that it consists of so- 
dium and chlorine ; if the name ends in ide the compound 
contains only the elements mentioned, which, except in 
a few cases, are but two in number. Thus, mercuric 
chloride contains mercury and chlorine; potassium io- 
dide, potassium and iodine. If the name of the com- 
pound ends in ate, with few exceptions which need not 
be mentioned here, the compound contains oxygen, in ad- 
dition to the other elements named. Thus, sodium chlo- 




Fig. 2. — Showing the "north" end of a magnetic needle being attracted by 
the "south" end of another. 

rate contains sodium, chlorine and oxygen; potassium 
sulphate, potassium, sulphur and oxygen. 

11. What Elements will Unite? — -Not every element 
will unite with every other element. If two magnets, 
either bar or horseshoe, be placed together, end to end, 
there will be no attraction if the two ends marked — 
are brought together or likewise if the two marked + > 
but if an end marked + be brought up to one with the 
opposite sign they adhere strongly. This is always true. 
Everyone is familiar with the ordinary compass, often 
spoken of as the mariner's compass. If the end of the 



A STUDY OF MATTER 



29 



needle which points north be approached by the north 
end of a similar magnetic needle, the one free to move 
will swing away; if the opposite end be approached they 
will attract each other. (See Fig. 2.) From these facts a 
simple law has been formulated: "Like poles repel and 
unlike poles attract each other. ' ' If the ends of two wires 
connected with an electric battery be dipped in a solution 
through which the current can pass in a U-shaped tube 
as shown in Fig. 3, the wire upon which the current 
enters is spoken of as the anode, from a Greek word 
meaning the road in and the wire upon which the current 
passes out is called the cathode, or the road out. Often the 




Fig. 3. — The wire marked + is the anode and the other is the cathode. 



anode is called the positive and the cathode the negative 
electrode. Now if the solution used be one of common 
salt, sodium chloride, it will be found that the sodium al- 
ways collects at the cathode and the chlorine at the anode. 
For this reason, applying the law stated above, sodium is 
regarded as a positive element and chlorine as a negative. 
In general, in all similar compounds the metal collects at 
the cathode and the other element at the anode. Hence, 
all such consist of a positive and a negative element 
or group of elements. In naming such compounds 
the positive is always given first. Thus, sodium chloride 
contains a positive element, sodium, and a negative ele- 



30 APPLIED CHEMISTRY 

ment, chlorine. Copper sulphate contains copper, a posi- 
tive element and a negative group, consisting of sulphur 
and oxygen. It would seem then from these statements 
that chemical union is a kind of electrical attraction. 

12. Chemical Changes, Kinds. — There are several 
kinds of chemical changes ; in all cases the identity and 
the characteristics of the substances involved are lost or 
destroyed. This has been illustrated in the case of hydro- 
gen and oxygen uniting to form water and of sodium 
and chlorine, to form common salt. Such as these are very 
simple and are known as "Additive Reactions," an expres- 
sion which indicates that the two substances have been 
added or joined together and have formed a single sub- 
stance. Another similar and very familiar case is that of: 
flashlight powders used in photography. The essential in- 
gredient, that which produces the intensely white light, 
is magnesium, a steel-gray metal which has been pow- 
dered. In burning, it simply combines with oxygen, pro- 
ducing a white compound known as magnesium oxide, 
often called magnesia, used in cleaning felt hats, kid 
gloves, as a dressing for white shoes and for similar well- 
known purposes. 

13. Simple Decomposition. — Another kind of chemical 
change equally simple as the preceding is known as 
"Simple Decomposition." In such changes the process 
is the reverse of the additive. A single compound by heat 
or some other force is decomposed into its component ele- 
ments. To illustrate by a familiar example, mercuric ox- 
ide, a compound whose name indicates its composition, if 
heated strongly is decomposed into mercury, which col- 
lects upon the sides of the vessel in which it is heated, 
and oxygen, which is invisible, but which may be detected 
by holding a pine splinter with a spark upon the end 
above in the outgoing current of gas. The splinter will 



A STUDY OF MATTER 31 

burst into a flame. Likewise, if a current of electricity 
be passed through water acidulated to render it a conduc- 
tor, it will decompose the liquid into the two gases of which 
it is composed. 

14. Metathesis, or Double Decomposition. — By far the 
greater number of chemical changes are not as simple 
as the two kinds already mentioned. More frequently 
two, and sometimes more than two, substances unite or 
react with each other, in which case both substances are 
decomposed and two or more new ones are produced, by a 
rearrangement of the elements contained in the com- 
pounds. Such a change is spoken of as "Metathesis" or 
"Double Decomposition." It may be illustrated by add- 
ing a few cubic centimeters of a solution of potassium io- 
dide to one of mercuric chloride in a test tube. Two new 
substances are formed, both entirely different from the 
original, one of them now a brilliant red color and not sol- 
uble in water. Numerous illustrations of this kind of 
change will be had from time to time. Really, metathesis is 
but a combination of the other two kinds of change in 
which both or all of the substances used are decomposed 
and the products combined in a new way. 

15. Mixtures. — A mixture differs from a compound in 
that the composing substances do not unite with each other 
as in additive reactions; neither is there any rearrang- 
ing of the elements into new groupings. Further, as a 
rule, no definite amounts of the two substances are used, 
or at least are not necessary. The particles of one inter- 
mingle with those of the other, but each retains all its 
own properties. White sand may be mixed with com- 
mon salt, but neither has lost its distinguishing properties. 
A little placed on the tongue will possess a salty taste and 
at the same time will have the gritty feeling of the sand. 
Moreover, one may readily be separated from the other 



32 APPLIED CHEMISTRY 

by adding water, stirring and after a few minutes decant- 
ing or filtering. A common case given by nearly all books 
is that of fine iron filings and flowers of sulphur. Mixed 
together, the result is a greenish-gray powder, but neither 
has lost its distinguishing properties, and as in the case 
of the salt and sand they may be readily separated. 
With patience most of the iron filings may be successfully 
separated from the sulphur by a good magnet. An easier 
and more satisf actory method is to add carbon disulphide 
which upon shaking will dissolve the sulphur as water will 
salt. The dissolved sulphur may then be poured off 
through a filter paper ; if the filings are washed with 
another portion of the carbon disulphide all the sulphur 
may be removed. By evaporating the liquid the sulphur 
may be recovered with all the properties it possessed be- 
fore. If, however, the intimate mixture be heated for 
some time strongly in a test tube, the resulting mass will 
be black instead of greenish, will not be attracted by the 
magnet as the filings were, and the sulphur cannot be re- 
moved by solution. Chemical union has taken place and 
we now have a compound of iron and sulphur, called iron 
sulphide. 

Exercises for Review 

1. Do you believe Aristotle's statement about the globe of sand? 
Give reason for your answer. 

2. At the present time how is scientific truth obtained? Can 
reason aid at all in the discovery of Nature's laws? Explain. 

3. What was the old idea regarding the relation of water to 
air? "What facts had they to cause such a belief? 

4. What is meant by transmutation? What led the ancient phil- 
osophers to believe in such a thing? Do you believe it possible? 
Why? 

5. What is matter? How many kinds can you find in this book? 
In this room? Give two old theories about the composition of 
matter. 



A STUDY OF MATTER 33 

6. "What was Boyle's idea of matter? What is the present idea? 
Is this necessarily the true idea? Explain. 

7. Define an element. How many are known? How many are 
liquids? Solids? How many constitute nearly the whole of the 
earth? What two are the most abundant? 

8. What is a compound? Name two and give composition. Ex- 
plain what is meant by chemical union. Illustrate. 

9. What is the general plan of naming compounds? Give the 
signification of the endings ide and ate. Give illustrations. 

10. Into what two classes are elements divided? Will copper 
and silver unite to form a compound? Give reason for your answer. 

11. How can one learn experimentally whether an element be- 
longs to one class or the other? Give meaning of the terms anode 
and cathode. What synonyms are sometimes used? 

12. Name three kinds of chemical changes. Give illustration 
of each. Show how the third may be regarded as a combination 
of the other two. 

13. How does a mixture differ from a compound? Name two 
mixtures and give some easy way of separating them. 



CHAPTER II 

WATER AND HYDROGEN PEROXIDE 

Outline — 

Forms of Appearance 
Characteristics of Pure Water 
Water in the Human Body and Foods 
Necessity of Water to the Body 
Proof of Composition 

(a) By Electrolysis 

(6) By Weight 
Law of Definite Proportions 
Water of Combination 

Hydrates 
Efflorescence 
Deliquescence 
Domestic Water Supplies 
City Water Supplies 
Hydrogen Peroxide 
Law of Multiple Proportions 

1. Its Familiarity. — Water is at once the most famil- 
iar of all natural substances and one of the most inter- 
esting. It appears in a very large variety of forms, all 
more or less familiar: in partially condensed vapor as 
fog; in the feathery cirrus cloud: the billowy cumulus, 
the beautiful summer cloud ; the stormy and threatening 
nimbus. In the solid form as snow. hail. ice. glaciers and 
icebergs. 

2. Characteristics of Water. — Pure water is tasteless, 
odorless and colorless, except in great depths as lakes 
and seas, when it appears blue or bluish green. It is 
often said that distilled water tastes flat, but this is be- 
cause we are accustomed to drinking water somewhat 
impure. Just as beans or potatoes or other vegetables 
served without salt would taste flat so does water with- 

34 



WATER AND HYDROGEN PEROXIDE 35 

out the usual impurities. Pure water when evaporated 
leaves no residue, hence would form no incrustation on 
the inside of kettles or boilers. 

3. Water in the Human Body. — Not only does water 
appear in such variety of form and such quantities in 
nature, but it constitutes a very large proportion of the 
animal body. Only about 40 per cent of the human body 
is solid matter, while in the lower animals the percentage 
of water is much higher. Our foods are also high in 
water content. Even butter and flour, which we often 
think of as dry, contain as much as 12 to 14 per cent of 
water for the former, and 10 to 11 for the latter. The 
following table will give an idea as to many of the com- 
mon food products: 

Table 

Per cent 

Beans, dry , 12.60 

Beans, string 89.00 

Bread, yeast 36.12-37.70 

Cabbage 91.50 

Carrots 88.20 

Cauliflower 92.30 

Celery 94.50 

Cheese 34.38-38.60 

Corn, dry 13.12 

Eggs 73.67 

Flour, wheat 10.11 

Meat, lean beef 67.00-70.00 

Meat, lean pork 60.00 

Meat, veal 73.30 

Mutton 50.20 

Oat Meal 12.37 

Peas, dry 12.62 

Peas, green 79.93 

Potatoes, sweet 75.00 

Potatoes, white 66.10-S0.60 

Eice 13.11 

Turnips 89.60 

Watermelons 92.40 



36 APPLIED CHEMISTRY 

4. Value of Water to Animals and Plants. — Nothing 
need be said about the value of water in the household. 
Life itself is impossible without it. to say nothing of 
the comfort it brings. Digestion is merely a process by 
which solid foods are made soluble that they may be 
carried through the blood to all parts of the body. As 
water is the most nearly universal solvent it enters 
largely into the process of digestion. Assimilation of 
food is impossible in the absence of water; and not only 
is this true, but most of the waste matter of the body 
is carried away dissolved in water or mixed with it in 
large amounts. On account of its high specific heat, that 
is. a given amount of water contains more heat energy 
than the same weight of any other liquid at the same 
temperature, it is regarded as the best means of wanning 
houses in severe weather. It is this very fact that tempers 
the winters in the Great Lake regions and along the 
oceans, and renders the climate of countries washed by 
the Gulf Stream and Japan Current far warmer than 
other countries in the same latitude not thus favored. 
In the human body, the blood, largely water, in constant 
circulation, tends to keep the body of perfectly uniform 
temperature. In summer, the body is cooled by the rapid 
evaporation of the water in the blood through the pores 
of the skin: thus, summer and winter, the water in the 
body serves to keep a uniform temperature throughout. 
To maintain the supply thus needed, an ordinary per- 
son requires from two to three pints of water per day. 
in summer more than in cold weather. Plants, likewise, 
must have water to enable them to absorb the necessary 
substances of food value from the soil, as also, to make 
the cellulose, starch and sugar, which they store up in 
their stems, seeds and fruits. 



WATER AND HYDROGEN PEROXIDE 



37 



5. Composition of Water. — By volume, water is com- 
posed of hydrogen, two parts, and oxygen, one part. 
This is usually shown experimentally by the Hoffman 
apparatus (Fig. 4). R is a reservoir into which the 
water is poured in filling the apparatus. It is neces- 
sary to use water slightly acidulated with some acid, as 
sulphuric, since pure water is not a conductor of elec- 
tricity. In filling the side tubes, B, B, the stop-cocks are 
carefully opened, one at a time, and the water allowed 
to flow in until it barely reaches the stop-cock level. 




Fig. 4. — Electrolysis or Hoffmann apparatus. 



Not much more should be put into R than will fill the 
three tubes, for a small amount of water makes a large 
quantity of gas and this forces the excess back into the 
reservoir, hence room must be left to receive it. Plat- 
inum strips, A, A, serve as electrodes and are connected 
with the source of current by means of wires sealed in 
glass tubes passed through the corks, C, C. When every- 
thing is ready the current is turned on ; bubbles imme- 
diately begin to rise from both electrodes, much faster 
from the cathode than the anode. After a few moments 



38 APPLIED CHEMISTRY 

the quantity of gas in each tube may be read from the 
graduations etched on the tubes, B, B. It Avill be found 
that the quantity of one gas is always 'double that of the 
other. To know that the smaller volume is oxygen, hold 
a splinter with a spark on the end over the tip of the 
tube and carefully open the stopcock. The pressure of 
the water in R will force the gas out and ignite the 
splinter. This characteristic test for oxygen has been 
mentioned in the preceding chapter. The usual method 
of testing hydrogen is by lighting it. A burning match 
or better, a small candle, brought to the tip of the tube 
containing the larger quantity of gas, will ignite it when 
the stop cock is cautiously opened. The flame at first 
will be invisible, or until the glass becomes red-hot; 
but a piece of paper held to it will be instantly ignited, 
thus showing the presence of a flame. 

6. Explanation of the Experiment. — Students fre- 
quently ask why the hydrogen goes to the cathode or 
negative electrode, and the oxygen to the anode. This 
will be readily understood if it is remembered what was 
said in the preceding chapter about compounds con- 
sisting of a positive and a negative element or group. 
Since oxygen belongs to what we call the negative 
group, it would necessarily be attracted to the anode: 
while hydrogen, being positive, would be attracted to 
the negative electrode. 

7. Proof of Composition by Weight. — Since gases are 
very light substances it is necessary to obtain their 
weights indirectly in this experiment. In Fig. 5 hy- 
drogen is obtained from any suitable generator, K, 
which for convenience may well be a Kipp apparatus. 
In order that the gas may be perfectly dry it is allowed 
to bubble slowly through a wash bottle, containing 
concentrated sulphuric acid, which is an excellent dry- 



WATER AND HYDROGEN PEROXIDE 



39 



ing agent in that it absorbs water readily. The tube, T, 
made of hard glass, contains copper oxide, preferably 
in what is known as the wire form. Before connecting, 
this tube with contents is carefully weighed. In the 
U-tube calcium chloride in small lumps is placed, the 
tube and contents carefully weighed and connected to 
the combustion tube as shown. The hydrogen is then 
turned on, the heat applied, gently at first, until the 
glass is well warmed, and the operation continued until 
the contents of C have become red like bright copper. 
The heat is then turned off, the hydrogen allowed to 
flow until the tube is cooled enough to handle comfort- 




Fig. 5. — Composition of water by weight. 

ably when both T and U with contents are again carefully 
weighed. What has happened is as follows: Hydrogen 
has the power of taking oxygen away from many oxides 
when heated strongly. It does so in this case and leaves 
in the combustion tube mostly pure copper. The loss 
of weight in this tube, therefore, is the weight of the 
oxygen used. The hydrogen and oxygen at the tem- 
perature present combine to form water, which in the 
condition of vapor passes over and is absorbed by the 
calcium chloride in tube U. The gain here, therefore. 
is the weight of the water produced. Subtracting the 
weight of the oxygen used from that of the water formed 



40 APPLIED CHEMISTRY 

gives the weight of the hydrogen. Allowing for experi- 
mental errors which are always possible, it will be found 
that the average of a large number of experiments car- 
ried out thus is always 8 parts of oxygen to 1 of hy- 
drogen. A typical case with data obtained by actual 
experiment is given below: 

Copper oxide and tube before heating 37.23 grams 

Weight of same, after heating 29.87 

Loss, which is oxygen 7.36 

Calcium chloride and tube, before heating. . . .25.18 
Weight of same, after heating 33.46 

Gain, which is the water 8.28 

Subtracting the oxygen from weight of wafer 0.92 
Ratio of oxygen, 7.36, to hydrogen, .92, is 8 to 1 

8. Law of Definite Proportions. — It was stated in the 
preceding chapter that a compound is a substance con- 
taining two or more elements united in a fixed and defi- 
nite-proportion by weight. The above experiment il- 
lustrates the definition and at the same (time shows 
proof. Out of this truth, which applies to all compounds, 
grows the "Law of Definite Proportions," which is 
usually stated thus: When two or more elements unite 
chemically to form a compound they always do so in the 
same fixed and definite proportion oy weight. Why they 
must necessarily do this will be taken up at another time 
in Chapter VI. 

9. Hydrates — Water of Combination. — All have seen 
various substances in crystalline form, such as rock 
candy, alum, blue vitriol, or such natural compounds as 
iron pyrite, silica, called rock crystal, and galena. Crys- 
tals of artificial compounds are usually prepared by dis- 
solving the substance in water and allowing the water 
to evaporate. When this occurs, very often a consider- 
able portion of the water combines with the dissolved 



WATER AND HYDROGEN PEROXIDE 41 

solid instead of passing off into the air. Sometimes the 
water thus combined weighs even more than the solid 
itself. The water thus taken up is called water of com- 
bination or sometimes water of crystallization, and the 
compound thus formed is called a hydrate. Familiar ex- 
amples of hydrates are blue vitriol, Epsom salts, alum, 
sal soda, and green vitriol. 

Table Showing a Few Hydrates and Amount of Water 
Alum, common. .45.57 per cent 

Blue Vitriol 36.14 

Borax 47.12 

Epsom salts 51.22 per cent 

Green Vitriol 45.32 

Sal Soda 62.93 

10. Efflorescence. — Hydrates may be regarded as true 
compounds, for they differ greatly in their physical 
properties from the anhydrous compound. Thus, ordi- 
nary hydrated copper sulphate is deep blue in color, and 
occurs in more or less regularly-shaped triclinic crys- 
tals. Anhydrous copper sulphate is white in color and 
when crystalline, which is not common, is in slender 
needle-like crystals. However, this combination is rather 
an unstable one. By heat, usually the water of the hy- 
drate may be removed without affecting the composi- 
tion of the remaining portion of the compound at all. 
Even at ordinary room temperatures in many cases con- 
siderable portions or all of the water of combination 
spontaneously passes off into the air. The extent of this 
loss depends upon the humidity of the air, the tem- 
perature and the specific rate of the particular compound 
itself. This may be seen in an interesting little experi- 
ment. A manometer as shown in Fig. 6 is attached 
to a side-neck test tube. A bent glass tube may serve 
as a manometer if no other is at hand. A rubber cork 



42 



APPLIED CHEMISTRY 



is fitted snugly into the test tube filled about half full 
of mercury. The bent tube also contains mercury at the 
same level in both arms. A crystal of some hydrate, 
such as sodium sulphate is put upon the mercury in the 
test tube and the cork carefully inserted again so as not 
to disturb the level of the mercury in the bent tube, M. 
Even at the room temperature water will escape from 
the crystal, producing pressure upon the mercury in the 
manometer, moving it up the longer arm, until there is 




Fig. 6. — Manometer, used in testing gas pressure. 

equilibrium. At this point no more water escapes from 
the hydrate on account of the pressure exerted upon 
it. Now, if the temperature be raised a few degrees, more 
water will be expelled and the mercury will rise in the 
outer arm still higher, until the added jDressure again 
equals the vapor pressure of the water in the crystal. 
Upon cooling the equilibrium is again disturbed and 
through the pressure of the mercury the hydrate will ab- 
sorb water vapor until there is again equal pressure within 
and without the hydrate. In the open air, as the pres- 
sure is not increased by the escape of the water, the loss 



WATER AND HYDROGEN PEROXIDE 43 

continues until no more can be driven off at that tem- 
perature. A considerable number of hydrates are able 
to part with all their water at ordinary room tempera- 
ture and usual atmospheric conditions. Such hydrates 
are said to be efflorescent. Efflorescence may be defined 
as the property which some hydrates possess of giving 
off to the air their water of combination and of crumb- 
ling to a powder. The word, literally translated, means 
becoming flowers or flour, that is, a fine powder. When 
efflorescence occurs, the crystalline structure of the sub- 
stance is destroyed and usually a powder results. Such 
hydrates as sal soda, often called washing soda, ferrous 
sulphate, and Glauber's salt, or sodium sulphate, are ex- 
cellent examples of efflorescent hydrates. 

11. Deliquescence. — Deliquescence may be defined as 
the property some substances have of attracting mois- 
ture from the air in such quantities as to be dissolved 
in it, The word means becoming liquid. Two such sub- 
stances have been mentioned already, used in the experi- 
ment for the determination of the composition of water 
by weight, sulphuric acid and calcium chloride. They 
have frequent applications in the chemical laboratory for 
drying gases. As calcium chloride is a by-product of cer- 
tain industries and very cheap, it has been tried by the 
United States government experimentally as a preventive 
of dust on roadways, instead of frequent sprinkling. Ob- 
viously it could not be used thus where there is much 
rain in the summer season, since, on account of its great 
solubility, it would be quickly washed away. Other good 
examples of deliquescent substances are caustic soda, of- 
ten called lye, and caustic potash. A hygroscopic sub- 
stance is one that will in damp weather absorb moisture 
from the air in sufficient quantities to become moist but 
not to liquefy. For example, common salt in our homes 



44 APPLIED CHEMISTRY 

often becomes clamp in rainy weather but it never lique- 
fies, hence is hygroscopic rather than deliquescent. 
Really, however, in this case the condition is due to the 
presence of a small quantity of a deliquescent substance, 
such as magnesium chloride, and not to the salt itself be- 
ing hygroscopic. 

12. Domestic Water Supplies. — Water is the most 
nearly universal solvent known. Glass, rocks and min- 
erals of all sorts, which ordinarily are thought of as in- 
soluble in water, when left for long periods in contact 
with water, do dissolve appreciably. This is the source 
of all mineral and hard waters. Organic impurities 
likewise and substances of all sorts are dissolved by 
water, so that especially in towns and cities, but in 
reality everywhere, the domestic supply of water must 
be carefully guarded. Cisterns, springs and wells in 
large towns and cities are never safe, and frequently 
not in smaller places. Sewage and seepage from cess 
pools make their way through the soil to all such 
sources of water and cause serious contamination. The 
water may be perfectly clear and tasteless, yet abso- 
lutely unfit to drink. Only chemical and bacteriologic 
tests can show and in case of doubt these should be 
applied. 

13. Rivers as a Source of Supply. — Probably more of 
the large American cities obtain their water supplies 
from rivers than from any other source. It would seem 
at first thought that such would be open to the greatest 
objection, because of the fact that they are the common 
means used by cities in disposing of their sewage, and 
are accessible to contamination in various ways. For- 
tunately, however, nature has a method of destroying 
such impurities. Exposure to the air in a flowing 
stream, especially if the bed be rocky so as to cause an 



WATER AND HYDROGEN PEROXIDE 45 

agitation of the water and to bring all portions of it 
to the surface, soon results in the destruction of most 
organic impurities. The city of Los Angeles obtains 
its water supply from the Owens River, bringing it over 
two hundred miles. When it enters the upper end of 
the San Fernando valley it dashes rapidly down in an 
open viaduct over a very rocky artificial bed, such that 
the water is churned into a foam, thoroughly impreg- 
nating it with air. A very noted case was brought to 
the attention of the public a few years ago when St. 
Louis brought suit in the courts against Chicago on 
the grounds that the latter city was contaminating the 
water supply of the former by conveying vast quantities 
of sewage through the Illinois River into the Mississippi 
not far above the intake of the St. Louis supply. Nu- 
merous analyses of the water were made, but bacteri- 
ologic and chemical tests failed to sustain St. Louis in 
her claims. Nevertheless, pathologic bacteria are able 
to withstand long exposure of this character and daily 
tests of city water must be made. If the water be 
muddy, as it may be more or less all the time, and very 
much so at certain seasons, further purification is nec- 
essary. Briefly stated, the steps are about as follows : 
The river water is pumped into huge basins or reservoirs, 
where a stream of lime water and another of a solution 
of alum or some other coagulant, are allowed to enter 
through pipes. These two solutions in meeting produce 
a coagulum or gelatinous precipitate which in settling 
carries practically all the mud with it. Naturally, as most 
of the bacteria present are attached to mud particles, they 
are carried down also. At intervals this accumulated 
deposit is washed back into the river. In very large cities, 
such treatment is usually supplemented by filtration ba- 
sins from which the water passes out through thick layers 



46 



APPLIED CHEMISTRY 



of sand and gravel as is shown in Fig. 7. Finally, before 
the water begins its journey to the mains of the city, 
either liqnid chlorine or a solution of bleaching powder in 
small quantities is introduced for the purpose of destroy- 
ing any pathologic bacteria which may remain. 

14. Lakes as a Source of Supply. — Many cities obtain 
their supply from lakes either natural or artificial. In 
such cases, unless the lake be large such as those upon 
which Chicago, Cleveland and other northern cities are 
located, another serious problem is confronted. A cer- 




Fig. 7. — Diagrammatic view of city water plant. B, the settling basin; F, 
the filter, in the bottom of which are layers of sand and gravel, indicated by 
the letters S and G. 



tain kind of algas, a species of plant to which the com- 
mon green scum seen upon stagnant ponds belongs, 
grows in the water and late in summer produces spores 
which upon bursting liberate a very offensive odor, so 
that the water cannot be used for drinking or cooking. 
It has been found that the presence of a minute quantity 
of some copper compound, as blue vitriol, will prevent 
the growth of such alga?. Accordingly, a burlap sack, 
filled with blue vitriol crystals, is suspended from a 



WATER AND HYDROGEN PEROXIDE 



47 



boat and is rowed back and forth across the lake in ev- 
er}- direction for hours or days, until the copper com- 
pound is dissolved. The amount of blue vitriol present 
is so small as to have no appreciable effect upon the 
human system, but is destructive to the algae. By some 
it is thought that the copper enters into combination 
with the albumin of the algae and settles to the bottom. 
If this be the explanation, then there is none left in the 




Fig. 8. — Roosevelt Dam, which is very similar to the one at Sweetwater. 

water. There are several cities of the southern states 
which have had to adopt this plan; but one of the 
most noted is that of Sweetwater Dam a few miles from 
National City and San Diego in southern California. 
It is a huge reservoir in a mountain valley, formed by 
a concrete dam and holds at its capacity several billion 
gallons of water. See Fig. 8, a typical dam for such 
water systems. 



48 APPLIED CHEMISTRY 

HYDROGEN PEROXIDE 

15. Composition. — In composition, lrydrogen peroxide, 
or dioxide, as it is often called, closely resembles water. 
Instead of having eight parts of oxygen to one of hy- 
drogen, as is the case with water, it has sixteen of oxy- 
gen to one of hydrogen. This added amount, however, is 
held very loosely, much as is true of the water contained 
by many hydrates. As a result, therefore, it is escaping 
at all times, unless in tightly corked bottles, which 
should be kept in a cool place. Even then the oxygen es- 
capes until sufficient pressure is attained in the bottle 
to produce equilibrium between the vapor tending to 
escape from combination and that of the air above. This 
explains why the cork comes out with a "pop" when it 
has not been previously removed for some time. Hy- 
drogen peroxide is put on the market in the form of a 
weak solution, usually about 3 per cent, not only under 
the name of hydrogen dioxide but also as dioxygen. 

16. Uses. — The value of dioxygen as an antiseptic de- 
pends upon the oxygen being continually liberated. Just 
as flowing water is purified by the oxygen of the air, 
so bacteria in wounds and diseased portions of the body 
are destroyed by this more concentrated or more active 
oxygen. It will be observed that when this additional 
amount of oxygen is removed from the dioxide, only 
water remains, which cannot cause irritation. Hence, 
hydrogen peroxide is probably the safest as well as one 
of the most efficient germicides for general use. It is 
also a good bleaching agent and is employed successfully 
for silks, wool, ivory, feathers and hair, animal prod- 
ucts which would be seriously injured by more power- 
ful agents such as chlorine. 



WATER AND HYDROGEN PEROXIDE 49 

17. Method of Testing". — The usual method of testing 
a solution of hydrogen peroxide is by adding a few drops 
of it to some starch mucilage or very thin paste to which 
has previously been added a very small quantity of 
potassium iodide solution. A deep blue solution re- 
sults. Another sensitive test is to add some potassium 
dichromate solution to one of hydrogen peroxide acid- 
ulated slightly with sulphuric acid. A deep blue color 
forms which lasts but a moment. It is not known what 
this blue substance is, because its temporary character 
prevents any examination of it. If some ether be added 
before putting the peroxide into the dichromate the 
deep blue compound is more permanent; by shaking, the 
ether layer may be made to take up most of the color, 
so that the test is thus intensified. 

18. Law of Multiple Proportions. — It has been seen 
that the composition of water is oxygen, eight parts, 
hydrogen one ; hydrogen peroxide, oxygen, sixteen, hy- 
drogen one. Thus two elements, uniting in different 
proportions, form two different compounds. In doing 
so, for a certain fixed amount of hydrogen the oxygen 
is twice as much in one case as the other, that is, it 
varies in a simple ratio. This has been found to be 
generally true and in chemical union for a fixed 
amount of one element, the other will always unite in 
some simple ratio as 1:2, 1:3, and the like. Dalton for- 
mulated this in what is known as the "Law of Multiple 
Proportions." Briefly stated it is, When two or more 
substances unite in different proportions to produce two 
or more different comipounds, for a fixed amount of one, 
the varying quantities of the other will always hear some 
simple ratio to each other. Later, reasons will be soon 
why this must necessarily be so, as was the case in the 
law of definite proportions. 



oO APPLIED CHEMISTRY 

Exercises for Review 

1. Xamo six different forms in which water occurs. 

2. Give the characteristics of pure water. Why does it taste 
"flat"? 

3. Give some idea as to the amount of water in the human body; 
also in many of our food products. 

4. Explain how water aids in digestion and assimilation; also 
how it aids in warming the body and equalizing temperature in 
summer. 

5. Describe the experiment showing analytic proof for composi- 
tion of water. Explain why the oxygen collects at the anode. 

6. Outline the experiment for proof of composition of water by 
w eight. 

7. State the ' ' Law of Definite Proportions. ' ' Illustrate. 

8. What is a hydrate? Water of combination? Give examples 
of hydrates. 

9. Define efflorescence. What is the cause of it? What is a 
manometer? Give some experiment using a manometer and its 
purpose. 

10. Define deliquescence. Xame four deliquescent compounds. 
What use? 

11. What is a hygroscopic substance? Why does salt become 
damp in wet weather? 

12. How do cisterns and wells become contaminated? Why 
are rivers apt to be purer than cisterns in a city? How are river 
waters clarified? 

13. What often occurs in small lakes used for water supply? 
How treated? 

14. Compare water and hydrogen peroxide. Give uses of latter. 

15. Give method of testing hydrogen peroxide. 

16. State "Law of Multiple Proportions." Illustrate. 



CHAPTER III 

OXYGEN AND OZONE 

Outline — 

Abundance of Oxygen in Nature 
Preparation in Laboratory 

Catalysis 
Characteristics 

(a) Physical 

(b) Chemical 
Uses of Oxygen 

(a) Respiration 

(b) Combustion 

(c) Medical and Others 
Oxidation, Combustion, Explosion 
Ozone, its Relation to Oxygen 
Preparation of Ozone 

(a) In Laboratory 

(b) For Commerce 
Characteristics 

(a) Physical 
(5) Chemical 
Uses 

1. Abundance of Oxygen. — Oxygen constitutes about 
50 per cent of all terrestrial matter. Of water it is 
eight-ninths by weight ; of the rocky crust of the earth, 
such as limestone, sand, sandstone, it is practically 50 
per cent ; of the air about 23 per cent by weight ; of the 
human body about two-thirds. Thus it is by far the 
most abundant of all the elements. Fig. 9 gives approx- 
imately the relative amount of oxygen and the seven 
other elements which constitute the greater part of the 
material of the earth. 

2. Preparation. — As far as known, Scheele, a Swedish 
chemist, first prepared ox} T gen about 1773, using man- 
Si 



52 APPLIED CHEMIST&Y 

ganese dioxide and sulphuric acid. However, he did not 
publish any account of his experiments for several 
years, and in the meantime Joseph Priestley, an English 
chemist, had in August, 1774, prepared and studied 
oxygen, making it by heating red mercuric oxide. It is 
interesting to know that he used as his source of heat 
a large lens or burning glass to concentrate the sun's 
rays and instead of the modern test tube he had a sawed- 
off gun barrel. Both of the above methods are still 
sometimes used, but there are much better ways. The 
most common method for obtaining oxygen in the labo- 
ratory is by heating potassium chlorate, mixed with 
manganese dioxide. The first named compound fur- 
nishes all the oxygen, although both contain it, but 



Oxygen 50 % 


Silicon 25 % 


E 

h 

3 

3 


1- 


s 
Is* 


HI 



Fig. 9. — Showing relative abundance of oxygen in nature. 

much less heat and time are needed if the mixture is 
used. By putting equal amounts of potassium chlorate 
into each of two test tubes and adding to one a small 
quantity of manganese dioxide, it is interesting to note 
that the mixture will give the oxygen test at the mouth 
of the tube in from one-sixth to one-fourth the time that 
is required for the other. Chemical tests show that the 
manganese dioxide is unchanged and rnay easily be recov- 
ered from the remaining mixture and used again. The ac- 
tion of any substance in thus hastening a chemical change 
is called catalysis, and the agent itself a catalyst or a 
catalytic agent. Many such cases will be observed from 
time to time in our study of chemical reactions. For exam- 
ple, it has been stated that hydrogen peroxide is a very 
unstable compound and owes its value to the fact of giving 



OXYGEN AND OZONE 



53 



off oxygen so readily. The addition of powdered metals 
or of charcoal, even in weak solutions, causes rapid decom- 
position of the peroxide. In a polished platinum dish a 
concentrated solution shows little evolution of oxygen, 
even at temperatures considerably above that of the or- 
dinary room ; but if the dish be roughened or scratched 
the decomposition becomes rapid. In all these cases, the 
powdered metals, the charcoal and the roughened plat- 
inum serve as catalytic agents in hastening the decom- 
position. 




Fig. 10. — Preparation of oxygen. 



The laboratory method of setting up the apparatus and 
of collecting the gas is shown in Fig. 10. The method is 
called collecting over water, and all gases not soluble in 
water may be collected in this manner. One precaution 
must be rigidly observed and that is, to remove the deliv- 
ery tube from the water before taking the heat away from 
the generator. A third method often used when only 
small quantities are wanted is by allowing water to drop 
slowly upon sodium peroxide, a compound sold under the 



54 



APPLIED CHEMISTRY 



name of "oxone." It gives off oxygen on the addition of 
water just as does hydrogen peroxide spontaneously. 

3. Characteristics of Oxygen. — Physical. — Oxygen is 
an odorless gas, slightly heavier than air, and in small 
quantities, is colorless. "When liquefied, as it may be at 
182° C. below zero, it is of a distinctly blue color. It is 
possible that what we speak of as the blue sky may be the 
color, at least in part, of the great depth of oxygen. It 
is soluble in water ; at 20° C, to the extent of 3 c.c. in 100, 
and in ice water about 4 c.c. in 100. In the liquid form 




Fig. 11. — Preparing oxygen from sodium peroxide. 



it is distinctly magnetic, as is shown by a suspended test 
tube of it being strongly attracted by a magnet. It may be 
solidified by surrounding with liquid hydrogen and is then 
a pale blue solid. 

Chemical Characteristics. — The most important chemi- 
cal property of oxygen is the vigor with which it com- 
bines with a large number of other elements, forming 
oxides. Charcoal, heated to redness, and lowered into 
a bottle of oxygen, glows brightly and if made from soft 
wood, it bursts into sparks. Phosphorus, ignited, in 



OXYGEN AND OZONE 55 

a deflagrating spoon, in oxygen burns with dazzling 
brightness, while iron in the form of wire or a watch 
spring burns with a beautiful shower of sparks. Sulphur 
and zinc both burn much brighter than in the air. All 
of these are additive reactions in which oxygen has com- 
bined with another element forming an oxide. Usually 
upon the sides of the bottle, in which the watch spring 
is burned, will be seen a reddish deposit of iron oxide, like 
rust, but most of the iron has been converted into what is 
called magnetic oxide and has dropped to the bottom of 
the bottle in the molten condition. The charcoal, being 
largely carbon, has produced carbon dioxide, and so on. 
Many of the oxides, like the one formed from sulphur, 
when dissolved in water give an acid test, and this fact 
gave oxygen its name, from the Greek words meaning 
acid former. 

4. Uses. — First of all should be mentioned its need in 
respiration. Aquatic animals breathe the small quantity 
of free oxygen dissolved in water, while land animals 
use the more concentrated form found in the air. Next 
to its value in respiration is its use in combustion. Or- 
dinary fire is impossible without oxygen; and without 
fire man must have remained little more than a savage. 
He could hardly have passed the advancement of the 
stone age ; the reduction of metals from their ores ; the 
making of steel tools; the locomotive, the steamship, the 
automobile, the airplane, all would have remained for- 
ever beyond him. Besides these two great uses there 
are many minor ones. The oxygen helmet is often used 
by firemen to enter places impossible otherwise ; by div- 
ers in exploring sunken vessels and for other under- 
sea work ; by rescuers after explosions in mines. The 
pulmotor is now a common appliance in the hospital, 
for inducing artificial respiration at critical times, such 



56 APPLIED CHEMISTRY 

as cases of asphyxiation, drowning, electric shock, and 
in crises of some diseases. 

5. Oxidation. — The uniting' of oxygen with any sub- 
stance is called oxidation, although, in the broadest 
sense, to the chemist the term means much more than 
this. The action may be slow, or so rapid as to be ac- 
companied by the generation of much heat. If suffi- 
ciently rapid to cause noticeable heat and light it is 
called combustion, but we shall see that combustion often 
takes place between substances when neither one is oxy- 
gen. Some substances, for example, oily waste or rags, 
absorb oxygen from the air : oxidation begins, and often 
sufficient heat is produced to ignite the rags. This is 
spontaneous combustion. It is never safe, therefore, to 
leave waste saturated with oils, especially drying oils like 
linseed, exposed long to the air. The manufacturers of 
the familiar cedar mop and others of like character, who 
use some kind of oil upon the cotton thread, provide a 
metal box to enclose the mop when not in use. At al- 
most every coal mine, the dump is seen to be on fire. Cer- 
tain iron compounds, when wet by rains and exposed to 
the air, begin to oxidize ; the temperature rises and even- 
tually is sufficiently high to ignite the small quantities 
of coal thrown out with the waste material. The fires 
in coal bins on shipboard probably often occur in the 
same way. A simple experiment illustrating spontaneous 
combustion may be made by dissolving a piece of 3 r ellow 
phosphorus the size of a pea in a cubic centimeter of car- 
bon disulphide and pouring the solution on a filter paper 
resting upon a ring stand. As soon as the carbon disul- 
phide has evaporated, which will be in a few seconds, ox- 
idation begins, followed very quickly by the ignition of 
the phosphorus. An instantaneous or nearly instantane- 
ous, combustion is called an explosion, In all cases. tfr§ to- 



OXYGEN AND OZONE 



57 



tal amount of heat produced is the same : in slow oxida- 
tions it is dissipated as fast as formed ; in explosions, the 
whole generated in an instant of time, causes enormous 
expansion of all gases produced and, as a result, tre- 
mendous pressures and often frightful results. 

6. Kindling Temperature. — The point at which com- 
bustion begins is called the kindling temperature. For 
phosphorus this is very low; for iron very high, with a 
great variety in between these two. A bit of yellow 




Fig. 12. — Boiling water in paper cup. 



phosphorus exposed to the air soon reaches its kindling 
temperature; a pile of shavings needs but the heat of 
a burning match; while anthracite coal must be fur- 
nished much kindling before it will burn. A little ex- 
periment giving some idea of the kindling point of pa- 
per, not essentially different from that of shavings, may 
be made by boiling water in an ordinary sanitary paper 
drinking cup, as shown in Fig, 12, In a few minutes the 



58 APPLIED CHEMISTRY 

water will boil vigorously, but as the temperature of the 
paper is not greatly above that of the boiling water it- 
does not catch fire. 

Ozone 

7. What Is Ozone? — Ozone is an unusual form of ox- 
ygen, always produced when an electric discharge takes 
place in oxygen or in the air. It is noticeable about the 
open arc in stereopticon work, in wireless telegraphy, 
and all similar places. The word ozone is from the 
Greek, meaning to smell and was given this gas because of 
its peculiar odor. It is often spoken of as an allotropic 
form of oxygen, which means another form. Many sub- 
stances appear in two or more distinct forms almost as 
different from each other as if they were not related at 
all; usually the rarer one, or more, are spoken of as the 
allotropes of the other, or the allotropic forms. 

8. Preparation of Ozone. — To secure sufficient ozone 
for a test, a stick of freshly scraped phosphorus partly 
submerged in water in a bottle is generally used. For 
the test, a strip of white paper dipped in some starch 
mucilage, to which has been added a very little of a 
solution of potassium iodide, is suspended in the bottle. 
In a short time the paper turns blue. The ozone has 
united with the potassium, has set the iodine free, and 
this has formed a solution with the starch which has a 
blue color. It is believed that ozone is also produced 
by other slow oxidations. It is probable, that, being a 
form of oxygen, ozone is always produced in the prep- 
aration of oxygen by any method. However, as we shall 
see later, ozone is a very unstable body, and if much 
heat is needed or produced in the method used for pre- 
paring oxygen, most of the ozone will be decomposed al- 



OXYGEN AND OZONE 



59 



most immediately into ordinary oxygen. By the meth- 
ods already suggested for the preparation of oxygen, by 
heating mercuric oxide or potassium chlorate, practi- 
cally no ozone is obtained. But if a method is used in- 
volving the application of no heat and in which no high 
temperature is reached through the chemical action, ap- 
preciable amounts of ozone ought to be present. Such 
a method may be tried by adding a few drops of strong 
sulphuric acid to a solution of potassium permanganate 




Fit?. 13. — Machine for making ozone. 



in water. The bubbles of oxygen may be seen coming 
up through the solution and the odor of ozone may be 
readily distinguished, often being sufficiently strong to 
irritate the throat. For commercial purposes ozone is 
now prepared by means of apparatus illustrated in Fig. 
13. The current from an induction coil spreads over the 
tin foil coating on the outside of the outer tube through 
which a stream of oxygen or air is slowly flowing, as indi- 



60 APPLIED CHEMISTRY 

cated by the two arrows at E and D. The electricity by 
brush discharge passes across to the tin foil coating on the 
inner surface of the other tube and out over the return 
wire. Thus, by a silent discharge of the current, little heat 
is generated and a very appreciable quantity of ozone is 
present in the escaping current of air. 

9. Characteristics. — Physical. — As already mentioned, 
ozone has a peculiar odor and is irritating to the throat 
and bronchial tubes, if present in considerable quantities. 
It is blue in color. It is much more soluble in water 
than oxygen; at 12° C. 100 c.c. of water will dissolve 
about 50 of ozone, while even at zero only 4 c.c. of oxygen 
would be dissolved by the same volume of water. Ozone 
is also very soluble in turpentine and this method is 
sometimes used to isolate it from other gases. Having a 
density one and a half that of oxygen indicates that 
three volumes of oxygen have been condensed to form 
two of the allotropic form. It liquefies at -119° C. If 
a current of ozone mixed with air be passed through a 
tube surrounded by liquid oxygen, the ozone is readily 
liquefied, while most of the oxygen will escape as a gas. 
Liquid ozone is deep blue in color and not transparent like 
liquid oxygen. 

10. Chemical Characteristics. — The most important 
chemical property of ozone is its strong oxidizing power; 
it is also very unstable. Mercury and silver both remain 
untarnished in pure air, but in ozone they are quickly 
darkened. It attacks many other substances much 
more actively than does ordinary oxygen. 

11. Uses. — Ozonized air, prepared as described in a 
preceding section, is now used in many photoplay houses 
of our cities as a means of vitalizing or purifying the 
air. Theoretically, it would seem to be an excellent 
plan, but in real practice there seems to be much doubt 



OXYGEN AND OZONE 



61 



on the part of some as to its efficiency. In some large 
flour mills, the wheat, after scrubbing, is passed still 
damp through ozonizers for destroying any traces of 
smut or mildew not removed by previous processes of 
milling. In some cities of Europe, ozone is used as is 
liquid chlorine in this country for purifying the water 
supplies. It is claimed that a gram of ozone, which 
if pure would be only about a half liter, or one pint, is 
sufficient to destroy as many as 30,000 bacteria per 
cubic centimeter in 1,000 liters, or 250 gallons. As there 
are 1,000 cubic centimeters in a liter, this would mean 
that a half liter of ozone or an equivalent mixed with 
air bubbled slowly through 250 gallons of water, would 
be sufficient to destroy thirty billion bacteria. 

Exercises for Review 

1. What part of the earth's crust does oxygen form? Give its 
proportions in several familiar things. 

2. What two men first prepared oxygen? What did they use? 

3. What is the usual method in the laboratory? Define cataly- 
sis. Name some other instance of catalytic action. 

4. Give its chief physical and chemical characteristics. How did 
it receive the name oxygen? What other names was it known by in 
an early day? 

5. Name the most important uses of oxygen. Give five minor 
uses. 

6. Define oxidation, combustion, explosion. How can you ac- 
count for spontaneous combustion? Give some case where caution 
must be exercised about the home. 

7. What is meant by the kindling temperature of a substance? 
Name one substance with very low kindling point: one with very 
high. 

8. Has water a kindling temperature? Give reason for your 
answer. 

9. What is ozone? Origin of its name? What is an allotrope? 



02 APPLIED CHEMISTRY 

10. Give two ways of preparing ozone and method of testing its 
presence. 

11. How is ozone prepared on a large scale? 

12. Compare ozone with oxygen. 

13. Give three uses of ozone. 

11. When a bellows is used to cause a fire to burn faster, is the 
action catalytic? Explain. 



CHAPTER IV 

HYDROGEN 

Outline — 

History of Hydrogen 

Occurrence 

Preparation 

(a) From Water 

(b) From Acids 

(c) From Oils 
Characteristics of Hydrogen 

(a) Physical 

( 1) ) Chemical 
Practical Uses 
The Phlogiston Theory of Combustion 

1. History. — It is presumed that Paracelsus, the great 
physician-chemist in the sixteenth century, discovered 
hydrogen, for he carried out experiments that involved 
the preparation of it. But he records no facts regard- 
ing it and may have overlooked it entirely. In 1766, 
Cavendish, an English chemist, prepared hydrogen and 
recognized it as a new substance but did not consider 
it an element. He called it inflammable air. Later when 
it was discovered that in burning, it produces water, it was 
given its present name which is from the Greek, meaning 
water producer. 

2. Occurrence. — It has been stated that hydrogen 
ranks ninth in abundance among the elements. In many 
ways, however, it is an important element. It consti- 
tutes as previously seen, one-ninth of the weight of 
water; it is an important constituent of nearly all or- 
ganic matter such as oils and fats, sugars, starches and 
the like; also of all acids, many of which are already 

63 



64 APPLIED CHEMISTRY 

familiar to the student. For example, acetic acid in 
vinegar, citric in lemons and grape fruit, oxalic in rhu- 
barb as well as several others, are well known. In the 
laboratory the most common acids are hydrochloric, sul- 
phuric and nitric. 

3. Preparation from Water. — The preparation of hy- 
drogen by the electrolysis of water has already been 
described. With the ordinary laboratory apparatus it 
is a slow process, but the gas obtained is very pure and 
sometimes this fact overbalances the lack of rapidity. 
Hydrogen may also be prepared from water by treating 
with some metal, as sodium or potassium. It may seem 
strange that a metal could do this. It has been seen al- 
ready that hydrogen belongs among the electropositive 
elements. It must be stated, however, that some ele- 
ments are much more positive in their behavior than 
others. Without attempting to be very exact, the ele- 
ments may be arranged and compared to the parts of 
a bar magnet, as illustrated in Fig. 14. If the magnet is 
laid down upon a sheet of paper upon which iron filings 
have been sprinkled, most of the filings will be at- 
tracted to the ends which are called the poles of 
the magnet, with the quantity rapidly diminishing 
toward the center. In a similar way the elements may 
be arranged in the order of their electropositive charac- 
ter, and those the better known to the student are thus 
shown in Fig. 1-1. It will thus be seen that hydrogen is 
well down the list. Naturally, therefore, such elements as 
potassium and sodium would be presumed to have the 
power of taking a negative element away from hydrogen 
and setting it free. Experiment shows that potassium does 
this violently, such that even on cold water the hydro- 
gen set free is ignited almost instantly and unless the 
piece of potassium is very small even it will burst into 



HYDROGEN 



65 



pieces from the heat generated. Sodium, though much 
less active, decomposes water rapidly, but unless the 
water is warm the hydrogen is not ignited. With mag- 
nesium the water must be hot for even moderate re- 
sults. In using sodium, since the metal melts almost 



K 

Na 
Ca 

Al 
Zn 
Fe 
Sn 
Pb 
H 
Cu 
Hg 

At 

Au 


■ 


n 







Fig. 14.— Electromotive series of metals and bar magnet with iron filinj 

attached. 



instantly when it touches the water, because of the 
heat generated by the chemical action, a gauze spoon 
is employed as shown in Fig. 15. The sodium is enclosed 
in this, inserted under the mouth of the test tube or 
bottle, which is filled with water and inverted over a 



66 



APPLIED CHEMISTRY 



trough of water, whereupon the gas rises and fills the 
bottle. It is a method somewhat expensive, but the gas 
obtained is pure. 

4. Obtaining Hydrogen from Acids. — As hydrogen 
may be expelled from water so it may be from acids, 
in a similar way and for the same reason. A very con- 
siderable number of metals might be used. Sodium 
and potassium would do, but their action is dangerously 
violent; hence, it should not be attempted. It is custo- 
mary to use some metal much farther down the electro- 
motive series, whereby the action is much slower. In 
the laboratory zinc is most often used either with hy- 




Fig. 15. — Preparing hydrogen from water by means of sodium. 



drochloric or sulphuric acid diluted. Iron is cheaper 
and is used when large amounts are desired, but the 
gas is not so pure as when zinc is employed. The metal 
in mossy form, is put into the generating flask and 
barely covered with water. When the receiving bottles 
are ready in the trough, the acid is added through the 
thistle tube a little at a time until action begins. The 
thistle tube must dip below the surface of the water 
in the flask (Fig. 16). 

5. Preparation of Hydrogen from Oils. — It is possible 
by heat alone to obtain hydrogen from such oils as kero- 
sene and similar oils, prepared from crude petroleum 



HYDROGEN 



67 



by distillation. But the gas thus obtained is only about 
50 per cent hydrogen, the remainder being a variety. 
Yet for some purposes even this is sufficiently pure and 
is exceedingly cheap. 

6. Characteristics of Hydrogen, Physical. — Hydrogen 
is an odorless, colorless gas, the lightest known. It 
is only about one-fourteenth as heavy as air, so that 
something over 11 liters are necessary to weigh 1 gram. 
It is a fairly good conductor of heat, which cannot be 
said of any other gas. It may be liquefied at a tem- 
perature of about -252° C. in which condition it is color- 
less. At -256° C. it becomes a solid. One of the most 




Fig. 16. — Preparation of hydrogen from acids. 



interesting of its physical properties is its ability of 
being absorbed by certain metals with the evolution 
of heat. This may be shown by the platinum sponge held 
over a jet of escaping hydrogen. In a very few seconds 
the sponge becomes red-hot and the hydrogen is ig- 
nited. It may likewise be shown by lowering the 
sponge into a bottle of hydrogen and oxygen mixed in 
about the proportions of 2 to 1. The sponge quickly 
becomes red and the gases explode violently. There 
is no danger, however, if a wide mouthed bottle is used. 
This property is often called occlusion. Palladium has 



68 APPLIED CHEMISTRY 

more remarkable powers for absorbing hydrogen than 
has platinum, in that it will take up nearly seven hun- 
dred times its own volume of the gas. Hydrogen read- 
ily passes through unglazed porcelain and cracks in bot- 
tles which would not leak water, and a cork made of plas- 
ter of paris is so porous as to offer little obstruction to the 
escape of the gas. For the same reason, toy balloons 
soon lose their buoyancy. 

7. Chemical Characteristics. — Hydrogen burns with a 
very pale blue flame with intense heat. If the delivery 
tube be glass, it is soon heated to redness, when the 
flame becomes visible, because of the constituents of 
the glass giving a yellow color. One gram of hydrogen 
in burning will produce more than four times as many 




Oxyhydrogen blowpipe. 



heat units as the same weight of anthracite coal. Water 
is the sole product of combustion. 

8. Practical Uses. — One valuable use is in the oxyhy- 
drogen blowpipe or torch as it is often called. It is il- 
lustrated in Fig. 17. The hydrogen enters through one 
pipe and the oxygen by the other, and near the point 
where ignited they are thoroughly mixed. The stop- 
cocks are so opened by the operator as to furnish twice 
as much hydrogen as oxygen. Intense heat is thus ob- 
tained, ranging in temperature from 2,000° to 2,500° C, 
at which platinum and other refractory metals are read- 
ily melted. If this flame be allowed to impinge upon a 
stick of lime, it gives a dazzling white light, called the 
calcium or Drwmmond light. Up to the introduction of 



HYDROGEN 69 

the electric arc, this was the best and commonly used light 
for stereopticons and stage effects. Another use for hy- 
drogen is in filling balloons. Especially during the world 
war was this extensive for dirigibles and for observation 
balloons. For some purposes natural gas may be used 
and has often been in flight contests, but it is eight times as 
heavy as hydrogen, hence does not compare in efficiency. 
However, its loss through diffusion would be much slower. 
For short flights, such as those seen at amusement parks 
and the like, the balloons are usually filled by heating 
kerosene or naphtha, as suggested in a preceding section. 
As this is often done by spraying the oil upon a bed of hot 
coals, there is usually some small amount of air present 
and some imperfect combustion resulting in the forma- 
tion of some smoke. For this reason, when the aeronaut 
leaps from the car in the parachute, a puff of smoke is 
often seen emerging from the capsized balloon. 

9. An Old Theory of Combustion. — Combustion is now 
well understood, but during the last quarter of the 
eighteenth century it was a matter of constant study 
and of much dispute. With the exception of Lavoisier, 
who lost his life at the time of the French Revolution, 
practically all the chemists of that day accepted the 
theory that a substance called phlogiston was contained 
in every combustible substance, and that it escaped as 
the substance was burned. The great French chemist 
never accepted this theory; and finally by the use of the 
balance, which up to that time chemists had not employed 
to any great extent, he succeeded in showing the fallacy 
of the phlogistic theory. It is now known that when a 
metal or any substance is burned, if all the products of 
combustion are saved and weighed, the total is greater 
than the weight of the original substance. Lavoisier 
called attention to this fact, and argued that it' something 



■f) 



APPLIED CHEMISTRY 



escaped, the resulting' oxides, or calces, as they were 
called iu that day. ought to weigh less. The upholders 
of the theory replied that, since phlogiston is an exceed- 
ingly light substance, it has a buoyant effect upon what- 
ever contains it. and therefore, the more there is the 




Fig. 18. — Lavoisier, beheaded in French Revolution, was the Father of 
Modern Chemistry. 



lighter the object. \Yhen hydrogen was discovered and 
its extreme lightness noted, as well as its great combusti- 
bility, many of the phlogistonists believed they had dis- 
covered phlogiston and regarded it as upholding' their 



HYDROGEN 71 

theory. But, in the light of what the balance continu- 
ally showed, they were finally obliged to acknowledge the 
fallacy of their position and that Lavoisier was correct. 

Exercises for Review 

1. Give a brief account of the discovery of hydrogen. How did 
it come to receive its present name? 

2. Name some very common substances containing hydrogen. 
How does it rank among the elements in total amount 1 ? 

3. Give two ways of obtaining hydrogen from water. What can 
be said about the value of these methods? 

4. What do you understand by the electromotive series of met- 
als? Where does hydrogen come in this series? 

5. How may hydrogen be obtained from acids? What metals 
are best? Why? What acids are generally used? Would nitric do? 

6. How may hydrogen be obtained from kerosene or gasoline? 
What is true of the purity of the gas thus obtained? 

7. Give the chief characteristics of hydrogen. Explain what is 
meant by occlusion. Give two experiments to illustrate. 

8. Give three important uses of hydrogen. What is the Drum- 
mond light? 

9. Give briefly the phlogiston theory of combustion. What was 
the most absurd tiling about this theory? Who finally overthrew it? 



CHAPTER V 

THE ATMOSPHERE 

Outline — 

Early Ideas of the Air 
Composition of Air 

Proportions 
Proof that Air is Mixture 
Diffusion of Gases 
Ventilation 
Purposes of the Constituents 

(a) The Oxygen 

( 1) ) Nitrogen 

(c) Carbon Dioxide 

(d) Water Vapor 
Humidity and Health 
Liquid Air 

Argon and Helium 

1. Early Ideas of the Air. — Even before the begin- 
ning* of the Christian era the air was an object of in- 
terest among philosophers. For centuries thereafter, 
however, little advancement was made in the knowledge 
concerning it, for the reason that no experimental stndy 
of it was attempted. In the latter part of the eighteenth 
centnry when the phlogiston theory was at its height 
a very considerable number of gases was discovered and 
the air itself received a very careful study in its rela- 
tion to combustion. Even thus, until near the end of 
the century, all the gases known Avere regarded as 
modifications of atmospheric air and were named ac- 
cordingly. Thus, Cavendish called hydrogen inflamma- 
ble air; Scheele called oxygen fire air; Priestley named 
it dephlogisticated air; Black, the discoverer of carbon 
dioxide called it fixed air; nitrogen was known as azote 

72 






THE ATMOSPHERE 73 

or phlogisticated air and so on. As we have seen it was 
Lavoisier who overturned, the prevalent ideas and sug- 
gested suitable names for some of the gases of recent dis- 
covery. 

2. Components of the Air. — In what is often spoken of 
as pure air there are always found nitrogen, oxygen, 
argon, carbon dioxide and water vapor, besides minute 
quantities of a few very rare elements. Sometimes the 
first three of these are regarded as the atmosphere 
proper, for the reason that they vary little; but when 
the evident purposes of the air are considered, the other 
two are essentials, and in the following study will be 
regarded as constituents. For years the air was believed 
to contain the two main gases in the form of a com- 
pound. At that time, the presence of argon was not 
known and the apparent unvarying proportion of oxygen 
and nitrogen led chemists to believe they were in com- 
bination. 

3. Proportions of These Constituents. — By volume the 
oxygen in the air constitutes about 21 per cent ; the ni- 
trogen, 78 per cent; the argon, a little less than 1 per 
cent — 0.94 — and the carbon dioxide, about .03 per cent, 
with the water vapor decidedly variable. If the air were 
of the same density throughout, it would extend above 
the surface about five miles. Then if the various con- 
stituents were arranged in layers about the earth, in 
accordance with their respective densities, there would 
be nearest the ground a layer of water about 5 inches 
deep; above that, one of argon, about 250 feet deep; 
then carbon dioxide, 12 or 13 feet; above that, oxygen 
one mile, and lastly the nitrogen, four miles. 

4. Proof That Air Is a Mixture. — There is very strong 
and convincing evidence now that air is a mixture. 
When pure distilled water is exposed to the air, al- 



74 APPLIED CHEMISTRY 

though the amount of nitrogen is about four times that 
of the oxygen, the oxygen absorbed is nearly double 
that of the nitrogen. If the air were a compound, the 
absorption of the two gases would necessarily be in the 
proportion in which they entered into the compound. 
Again, air is now readily liquefied. When this hap- 
pens the carbon dioxide and the water vapor solidify 
and precipitate out. A vessel of liquid air left standing 
shows, when about four-fifths of it has boiled away, 
that the residue is nearly pure oxygen. This would be 
possible only if the air were a mixture and the boiling 
point of nitrogen lower than that of oxygen. Alcohol 
in boiling gives off vapor of the same composition as 
the liquid and so does every liquid compound. Air, 
therefore, cannot be a compound. Again, every com- 
pound consists of two or more elements in unvarying 
proportions. In the air the oxygen may vary as much 
as three-fourths of 1 per cent. Not only these, but other 
proofs make it sure that the air is a mixture and not 
a compound. 

By weight the constituents are — 

Nitrogen 75.46 per cent 

Oxygen 23.18 ' ' 

Argon 1.29 " 

Carbon Dioxide 03 to .01 " 

Water Vapor Variable 

Other rare Gases. . .Very small amounts 

5. Diffusion of Gases. — If in a tall cylinder nearly 
filled with water, colored blue with litmus, a few cu- 
bic centimeters of sulphuric acid be introduced be- 
low the water by means of a pipette, in two or three 
days the heavy acid will have moved upward through 
the entire mass of water. This will be known by the 
litmus solution turning red, as it does in the pres- 



THE ATMOSPHERE 75 

ence of any acid. Likewise any gas tends to occupy 
all the space afforded it. If a cylinder of ammo- 
nia be inverted over one of hydrogen chloride, al- 
though the lighter gas is above one more than twice 
as heavy, in a very few minutes the two will be evenly 
distributed throughout the entire space, as can be seen 
by the action which takes place. This shows that the 
particles of a gaseous body are apparently moving in 
all directions all the time regardless of their density. 
This explains largely why the air is always a practically 
uniform mixture. Equilibrium is constantly being de- 
stroyed by various processes of nature and otherwise, 
but diffusion, as this movement is called, aided by wind 
currents, keeps the composition practically constant. 

6. Value of Each Constituent. — It has been stated in 
a preceding chapter that oxygen is necessary for respi- 
ration. When taken into the lungs it enters into a loose 
combination with the hemoglobin and is by the circu- 
lation taken throughout the body. Meeting the carbon 
in the various tissues, carbon dioxide is formed and by 
the oxidation heat is produced. Thus the body is warmed. 
In aquatic animals where the only oxygen attainable 
is the small amount dissolved in the water, the quantity 
of carbon consumed in the tissues is small, and thus 
little heat is produced. Such animals are "cold 
blooded"; naturally, therefore, the food required to 
sustain life is small in proportion. A good comparison 
may be had by noting the amount of food consumed 
by a canary bird and a gold fish of about the same 
weight. The human body of average size consumes 
daily about 750 grams or 26 ounces of oxygen. This 
is the equivalent of the entire amount of oxygen con- 
tained in over 2,600 liters of air. From this is produced 
carbon dioxide to the amount of about 2.2 pounds or 



ib APPLIED CHEMISTRY 

1,000 grams. When the air leaves the lungs at each 
respiration only about 16 per cent of oxygen remains 
instead of the original 23 per cent, while the carbon 
dioxide in the exhaled breath is present to the extent 
of about 4.1 per cent or more than 100 times as much 
as is contained in ordinary air. 

7. Ventilation. — It is apparent from the above how im- 
portant good ventilation becomes. This importance is 
emphasized when it is remembered that while the first 
respiration of a given volume of air removes over one- 
fourth of the oxygen, the second inhalation of the same 
volume of air only takes about the same proportion of 
what remains. Thus the body in obtaining impoverished 
air is not receiving anything like the amount needed. 
Lack of proper ventilation is most apt to be found in 
school rooms or other places where people congregate 
in considerable numbers, as photoplay houses, theaters, 
and the like. Health boards in many cities require that 
means shall be provided for furnishing 30 cubic feet of 
fresh air per minute per individual. In the ordinary 
home where the family is small there is no special pro- 
vision needed, for even in cold weather when doors and 
windows are closed there is sufficient leakage to fur- 
nish an abundance of fresh air. It is only in poor 
tenement houses and basements used as homes, where 
large families are often found, that the lack of ventila- 
tion is apparent in the home. 

8. Value of the Nitrogen. — To the human body, nitro- 
gen, as it exists in the air in a free state, seems to serve 
no other purpose than to dilute the oxygen. A fish out 
of water dies, partly probably because of the very rich 
atmosphere it is compelled to breathe. In the same way 
the human body, as at present constituted, could prob- 
ably not inhale pure oxygen continuously without un- 



THE ATMOSPHERE 



77 



due stimulation and serious results. In the combined 
form nitrogen enters into the muscular part of the body 
and only through the use of nitrogenous foods can its 
waste be repaired. Neither animals nor plants, as a 
general rule, can obtain nitrogen directly from the air, 
at least in sufficient quantities to meet their necessities. 
Animals secure it mainly through lean meats or legu- 
minous foods such as beans, peas and the clovers. Most 
plants in continuously cultivated fields obtain their 




Fig. 19. — Nodules in which the nitrogen-fixing bacteria live on the roots of 
a bean. (From Warren — Elements of Agriculture.) 



needed supply through fertilizers, which are largely ob- 
tained from the waste eliminated by the animal economy. 
So it will be seen there is an endless cycle existing here 
in which animals and plants each supplement the needs 
of the other. It should be stated, however, that there 
is one class of plants which, fortunately, is able through 
the aid of bacteria to obtain the nitrogen needed di- 
rectly from the air. These are the legumes, and agricul- 



78 APPLIED CHEMISTRY 

turists at present are employing this means extensively 
in restoring the needed nitrogen to the soils. The accom- 
panying figure shows the nodules upon the roots of a 
bean plant, formed by the nitrogen fixing bacteria. 
(Fig. 19.) 

9. Carbon Dioxide. — It will be learned later that car- 
bon dioxide is an inert gas as far as the human system 
is concerned, in that it is devoid of toxic effects. It is 
true, however, that a considerable quantity of it in the 
air usually indicates the presence of other substances 
deleterious to health. This is especially true if the air 
be impoverished by frequent respiration and therefore 
abounding in the waste materials thrown off from the 
body. It is this condition mainly that proper ventilation 
seeks to avoid. Health experiments carried out in such 
places as breweries, where considerable amounts of car- 
bon dioxide are continually escaping into the air, show 
that, other conditions not being unfavorable, headache 
and drowsiness, usually apparent in poorly ventilated 
rooms, do not occur and no unfavorable results follow. 
To plants, carbon dioxide is as essential as oxygen to 
animals. The leaves, corresponding to the lungs of the 
body, absorb the carbon dioxide and under the influence 
of sunlight are able to decompose it. In the plant labor- 
atory the carbon is combined with the water obtained 
from the soil and cellulose results to build the woody 
structure of the plant or tree. Another arrangement 
by another plant produces starch or sugar and a great 
variety of other well-known substances. But they all 
come primarily from the carbon dioxide obtained from 
the air through the leaves and must have the heat and 
light of the sun for the process. It is seen, therefore, 
as in the case of the nitrogen, that there is an endless 
cvcle in the transference of carbon from the animal to 



THE ATMOSPHERE 79 

the vegetable world and back again, and that the ex- 
istence of either without the other would in all proba- 
bility not be of long endurance. 

10. The Water Vapor. — It has been stated that the 
water vapor in the air varies greatly. The amount that 
can be held is dependent upon the temperature. At 
0° C. a cubic meter, which is something more than a cubic 
yard, is able to hold only 4.87 grams of water: at 10° 
C. it can hold 9.92 grams; at 20°, which is but little 
cooler than ordinary room temperature, 17.16 grams. 
For health, from two-thirds to three-fourths of the 
amount specified at room temperature is regarded as 
best; more than this, if the temperature be high, is op- 
pressive. The reason is that the human body regulates 
its temperature by the evaporation of water through 
the pores of the skin. A single gram of water for its 
evaporation requires something like 550 calories of heat; 
an ounce of water, which is about 28 grams, in being 
evaporated from the surface of the human body, would 
reduce the temperature of the entire body of 150 pounds 
weight about .5 of a degree. Anything therefore, which 
prevents or retards evaporation prevents the cooling 
of the body. When the humidity is high, as it often 
is in summer in the Atlantic, Gulf and Mississippi Valley 
states, the air surrounding the body is already nearly 
saturated with moisture. This greatly retards evapora- 
tion, and interferes with the regulation of the body 
temperature. 

11. Moisture and Health.— The public has been more 
or less well informed as to the importance of fresh air ; 
but the humidity of the air in the home in winter has 
not been greatly considered. As stated already, air at 
0° C. or 32° F. can hold only 4.87 grams of water vapor. 
Usually there is present not one-half this amount. This 



80 APPLIED CHEMISTRY 

air is taken into our homes, warmed to 20° or 21° C. or 
about 70° F., without the addition of any appreciable 
amount of water. The result is a condition decidedly 
adverse to health. Unduly dry nasal passages, irritated 
throat and bronchi, susceptibility to colds, chapped 
hands and skin and other evils follow. The question of 
humidity is now carefully considered by architects in 
the construction of large school buildings and the mois- 
ture content of the air is kept reasonably uniform by 
artificial means. In the homes like provision should be 
made. As it is not provided by the usual methods of 
construction and heating, the individual must do this 
himself. In rooms heated by radiators, either steam or 
hot water, a towel suspended from a rack, fastened 
behind the radiator and dipping in a pan of water sit- 
ting on the floor, will be out of sight and will furnish 
ample moisture. With hot air furnaces the problem is 
more difficult. It may be partially met by putting shal- 
low pans of water beneath each register where such are 
located in the floor. When not, each case with its pos- 
sibilities must be taken up by itself. It is a problem 
the student should interest himself in for the benefit 
of everyone in the home. 

12. Liquid Air. — For some years air has been lique- 
fied in commercial quantities. The principle underly- 
ing is that ordinary gases expanding from great pres- 
sure into a more or less perfect vacuum are cooled. In 
the apparatus used, this cooled, expanded air is com- 
pelled to pass out around the pipe through which the 
compressed air is entering. Thus at each impulse of 
the pump, cooler and cooler portions of air are forced 
out around the incoming supply, until eventually the 
point of liquefaction is reached. It is a colorless liquid, 
like water, and usually consists of 50 per cent or more 



THE ATMOSPHERE 81 

of oxygen instead of 23 per cent as in the atmosphere. 
The reason is that the boiling point of nitrogen is 194° 
C. below zero, while that of oxygen is 11% degrees 
higher. Thus from the constant loss of the nitrogen 
through evaporation the proportion of oxygen continu- 
ally increases the longer the vessel stands. Liquid air is 
kept and shipped in what are called Dewar bulbs, shown 
in Fig. 20. They are the original of what the public 
knows as thermos bottles, being double-walled flasks with 
a vacuum between and the walls coated with silver. 

13. Argon and Helium. — It has long been known that 
nitrogen prepared from the air is heavier than samples 
made from various nitrogen compounds. This led to 





Fig. 20. — Dewar bulbs. The thermos bottle is merely different in shape. 

the suspicion that there was some heavier gas mixed with 
it, Even as early as the latter part of the eighteenth 
century, Cavendish, the discoverer of hydrogen, was 
convinced that atmospheric nitrogen contained another 
gas and attempted to prove it experimentally. In elim- 
inating the nitrogen he had as a residual gas only a 
small bubble which he concluded to disregard. He prob- 
ably used too small quantities of air, for Ramsey, in 
1894, by practically the same experiment succeeded in 
obtaining sufficient quantity of the argon to prove it 
was the same gas he had obtained by another method 
of separating it from nitrogen. It is an inert gas and 



82 APPLIED CHEMISTRY 

received the name "argon" from a Greek word, meaning 
lazy or inactive. No compounds of argon are known. 

14. Helium. — The word is derived from the Greek for 
sun, and the name was given to this element because be- 
fore it was known upon the earth a line in the orange 
band of the solar spectrum was observed which belonged 
to some undiscovered element. Later, it was discovered 
in certain spring waters; it may be obtained from cer- 
tain minerals, compounds of uranium and thorium and 
is found in minute quantities in the air. It is a gas which 
is harder to liquefy than is hydrogen, having a boiling- 
point of -268.5° C. It is only twice as heavy as hydro- 
gen and unlike hydrogen is not combustible. It forms no 
known compounds. It is admirably adapted for filling 
balloons and dirigibles, and during the latter part of the 
war the United States was making great efforts at dis- 
covering some method of preparing it in commercial quan- 
tities. Not until too late was such a method devised. It 
is still a secret of the war department. 

Exercises for Review 

1. Name some of the gases discovered during the latter part 
of the eighteenth century and the names applied to them. Why 
were they given such names? 

2. Name the five components of the air. Give their proportions 
by volume and by weight. In what condition are they, free or com- 
bined? 

3. Give three or four proofs that the air is a mixture. 

4. What is meant by diffusion of gases? What effect does dif- 
fusion have on the homogeneity of the air ? 

5. What is the use of oxygen to the human body? Why are most 
aquatic animals cold blooded? Why is the whale not? Explain 
how the body is warmed. 

6. How much oxygen is removed from the air at each respira- 
tion? How many cubic feet per minute are needed for an indi- 
vidual? 



THE ATMOSPHERE 83 

7. Of what use is the nitrogen of the air to the body? How are 
the muscles repaired? Describe the nitrogen cycle. 

8. How are legumes different from most other plants? What 
gives them this power? 

9. What do considerable quantities of carbon dioxide in a room 
indicate? Is it deleterious to health? 

10. Describe the carbon cycle between plants and animals. What 
use do plants make of carbon? Of what use to animals? 

11. What governs the amount of moisture the air can hold? 
What is meant by saturated air? How much more moisture can 
air at ordinary room temperature hold than at zero? 

12. Why is a humid atmosphere oppressive in summer? 

13. What effect does an excessively dry atmosphere have upon 
the body? 

14. Give some methods of increasing the humidity in the home 
in winter. 

15. Give the principle underlying the liquefaction of air. What 
is a Dewar bulb? 

16. Describe liquid air. 

17. Hoav did argon come to be discovered? Who was first to at- 
tempt its discovery? Who finally discovered it? 

18. How did helium receive its name? Where is it found upon 
the earth? Of what special value will it be in large amounts? 



CHAPTER VI 

GASES AND SOME GAS LAWS 

Outline — 

States of Matter 

Charles' Law and Absolute Zero 

Applications of the Law 
Boyle's Law 

Correction for Changes in Temperature and Pressure 
Aqueous Tension 
Deductions from these Gas Laws 

O) The Molecular Theory 

(6) Molecular Motion 

(c) Gas Pressures 
The Atomic Theory 
The Corpuscular Theory 
Atomic and Molecular Weights 
Avogadro 's Hypothesis 
Atomic Structure of Molecules 
Determination of Molecular Weights 
Gram Molecular Weight 

1. States of Matter. — We are familiar with water in 

three conditions : solid — ice ; liquid — water ; gas, as 
steam. It has been stated in preceding chapters that 
oxygen, hydrogen and other gases may also exist in 
these three states. There are two forces present in ev- 
ery body: cohesion, an attractive force, tending to hold 
its particles together, and heat, a repellant force, tend- 
ing to expand it, or to separate its particles. Hence, when 
heat is applied, first the body expands, then if capable 
of doing so, it melts, and on the continued addition of 
heat the liquid vaporizes with very great expansion. 
Removal of the heat reverses the process. In gases, 
therefore, the repellant force is in the ascendancy ; in 

S4 



GASES AND SOME GAS LAWS 



85 



solids, the cohesive force. Solids and liquids upon being 
heated expand very irregularly; but gases are practi- 
cally constant and their behavior is described by cer- 
tain clearly denned laws. 

2. Charles' Law. — Experiment shows that any gas if 
heated from 0° C. to 1° above, expands 1/273 of its vol- 
ume at zero. Thus, if at the beginning there were 273 
c.c, at 1° C. there would be 274 c.c. ; at 10° C. 283 c.c. ; 
at 100°, 373 c.c. Likewise, if cooled below zero, at 



t-459- 



-] 373 +] Boiliny Poini 



Freezinq Pi. 



Fig. 21. — Comparison of thermometers. 



- 10° C, there would be 263 c.c, at 100° below, 173 c.c. 
Theoretically, therefore, if a gas were cooled 273° below 
zero its volume would have decreased to zero. But all 
gases become liquids before reaching this temperature; 
oxygen at -182.5°, hydrogen at -252.6°, helium at 
-268.5° and thereafter the contraction is very slight 
for each degree. The point, 273° below zero is known as 
absolute zero. While it does not mean the elimination of 
the substance, for that is unthinkable, it may be assumed 



86 APPLIED CHEMISTRY 

to mean the temperature at which there is no longer any 
heat in the body. In the liquefaction of helium, that 
point has been very nearly reached. It must be seen 
then that the volume of a gas varies as the absolute 
temperature. Charles' law states this fact thus: The 
volume of a gas, pressure remaining constant, increases 
or decreases directly as the absolute temperature. The 
absolute thermometer is not a manufactured article, but 
its degrees are the same as on the Centigrade scale, and 
it must be used in all problems involving Charles' law; 
hence Fig. 21 is given to make the method clear. Thus 
the boiling point of water would be 373° absolute and of 
melting ice 273° absolute. 

3. Value of Charles' Law. — Gases for the sake of con- 
venience are measured in volumes, but as they change 
greatly under varying conditions some standard must 
be adopted. For temperature this is the freezing point 
of water — zero Centigrade. However, as in actual work 
gases are seldom obtained at this temperature, their 
volume must be calculated from the measured volume. 
Knowing that they increase 1/273 for every degree 
raised above zero, this is not difficult. Putting Charles' 
law into a proportion we have 

V : V ::T : T' 

In which V is the original volume and V the new vol- 
ume, while T is the original temperature, absolute, and 
T' the new temperature absolute. In the form of an 
equation this reads, 

VT' = V'T 

from which either volume or temperature may be calcu- 
lated, knowing the other factors. To make the process 
clear, suppose we have in the laboratory a bottle hold- 



GASES AND SOME GAS LAWS 87 

ing 800 c.c. of oxygen, with the temperature 15° C. and 
without any change in pressure the temperature was 
raised to 22°. It is desired to know the new volume. 
Changing 15° C. and 22° C. to absolute temperatures, 
we have 273 + 15 = 288 and 273 + 22 = 295. Substi- 
tuting we have 

800 x 295 = V x 288 

800 x 295 
288 
from which the value of V, or the volume at 22° will be 
known. 

4. Boyle's Law. — It was formerly believed that liquids 
and solids could not be compressed; it is known now, 
however, that they may be, but as is true in variation of 
temperature they obey no law. Gases, on the other 
hand, are practically constant, a fact which was dis- 
covered by Robert Boyle and formulated by him in this 
law: The volume of any gas, provided the temperature 
remains constant, varies inversely as the pressure. In- 
versely means that if the pressure be increased the volume 
is diminished correspondingly and if the pressure be de- 
creased the volume increases in the same ratio. Put into 
mathematical form it is stated thus : 

V : V : : P' : P 

in which V and V have the same signification as stated 
under Charles' law and P and P' are the original and 
new pressures respectively. In the form of an equation 
the proportion becomes 

VP = V'P' 

which leads to another statement of the law, thus: The 
product of the volume of any gas multiplied by its pres- 
sure, always assuming that the temperature is constant, 
is a constant quantity. To illustrate, suppose Ave have 



88 



APPLIED CHEMISTRY 



200 c.c. of oxygen in a bottle at 15 pounds' pressure to 
the square inch. The product of the volume and pres- 
sure, V x P, or 200 x 15, is 3,000. If the pressure be 
doubled, according to Boyle's law, the volume now would 
be 100. The product of V by P', or 100 x 30 is 3,000, 
the same as before. Hence the statement that the vol- 
ume of any gas multiplied by its pressure is always equal 




Fig. 22. — Aneroid barometer. 



to its volume at any other time multiplied by the pressure 
at that time ; in other words, the product is a constant 
quantity. 

5. Pressures, How Stated.— In most practical prob- 
lems involving Boyle's law the changes are those of at- 
mospheric pressure only. The amount of such pressure 
is obtained by the use of the barometer, which for the 



GASES AND SOME GAS LAWS 89 

sake of convenience is read in units of length and not 
weight. In the aneroid barometer, shown in Fig. 22, the 
figures on the dial indicate inches, while the smaller 
divisions are millimeters of which practically 760 equal 
30 inches. In the mercurial barometer at sea level, 
the pressure of the air supports a column of mercury 
30 inches in height or, in other words, the weight of 30 
inches of mercury. But as the weight of 28 inches of 
mercmy would have the same mathematical relation to 
the weight of 30 inches of mercury as 28 inches to 30 
inches, and as length can be read immediately from the 
barometer, in all problems it is customary to use linear 
units, and those of the metric system ; that is, millimeters 
or centimeters. To illustrate : Suppose the barometer 
reads 750 mm. and we have in a bottle standing over 
mercury 500 c.c. of gas, and wish to know the volume at 
standard pressure, which means pressure at sea level, or 
760 mm. pressure. Substituting in the formula, 

VP = V'P', 

we have 500 x 750 = V x 760 

500 x 750 
V = 



760 

in which V will be the true volume at one atmosphere's 
pressure. 

6. Corrections for Pressure and Temperature.— In 

practical work often both pressure and temperature 
have changed during the time of an experiment. In 
such cases calculation must be made to correct both. 
This may be done in two steps, by finding the volume 
resulting from one change, either pressure or tempera- 
ture, and then using this in the other equation. In fact 
beginners may find all such problems easier if solved by 
analysis instead of by use of formula given. At any 



90 APPLIED CHEMISTRY 

rate the method has the advantage of appealing to the 
reasoning powers at every step and on that account 
is good. It must be evident that increased pressure 
would cause decreased volume. Hence the original 
volume must be multiplied by a fraction greater or less 
than one as the change in pressure would cause increase 
or decrease in volume. Thus, if we have 500 volumes of 
gas at 760 mm. pressure and wish to know what it would 
be at 780, we must ask ourselves, whether the volume is 
increased or decreased. As the pressure is greater, the 
volume would be less: hence the original 500 cubic centi- 
meters must be multiplied by 760/780 which will give a 
result less than 500. In the same way Charles ' Law may 
be applied. Increase in temperature causes increase in 
volume. Thus, remembering that absolute temperatures 
are always used, suppose we have 500 c.c. of gas at zero 
Centigrade and wish to know its volume at 20 degrees 
above: we must first change Centigrade readings into 
Absolute. In this case they would be respectively 273 
and 293. As the volume is increased the 500 c.c. must 
be multiplied by the fraction 293/273 which will give a 
value greater than 500. In case both temperature and 
pressure change, the result obtained in one of the above 
operations must be used as the original volume for the 
next. 

It is somewhat simpler, however, to use a combined for- 
mula, VPT' = V'P'T, 

in which the letters mean as previously stated. To il- 
lustrate its use : Suppose we have 500 c.c. of hydrogen 
over a trough of mercury at a temperature of 21° C. 
with the barometer reading 740 mm. It is desired to 
know the volume at standard conditions, that is zero 
Centigrade and 760 mm. pressure. Substituting in the 
formula VPT' = V'P'T, we have 



GASES AND SOME GAS LAWS 91 

500 x 740 x (273 + 0) = V x 760 x (273 + 21) 
500 x 740 x 273 
760 x 294 
The value of V' will be the true volume. In a similar 
way we might find the value of T' or P' or any other 
factor provided the others were known. 

7. Correction for Water Vapor. — In the laboratory 
gases are usually collected over water and hence con- 
tain some vapor. To learn their true volume at standard 
conditions, correction must be made for this. It has been 
found that at any given temperature the vapor, passing 
off from an enclosed vessel of water, will exert a definite 
pressure, always the same for that particular tempera- 



AIR PRESSURE 




Fig. 23. — Illustrating pressure of water vapor. 

ture. In Fig. 23, suppose we have a volume of gas with 
the water at the same level inside and without the bot- 
tle. Obviously the pressure within and without must 
be the same. On the outside the pressure is due to the 
weight of the air resting upon the water. Inside, the 
pressure results mainly from the gas enclosed!, buit 
partly from the vapor mixed with the gas. To know 
the real pressure of the gas, that of the vapor, which is 
spoken of as aqueous tension, must be subtracted from 
the total pressure. To illustrate : Suppose the gas in the 
bottle measures 900 c.c. and the barometer reads 750 mm., 
and the thermometer, 20° C. The aqueous tension at 20° 



92 



APPLIED CHEMISTRY 



is about 17 mm. : hence, the pressure which the gas within 
the bottle is exerting is 750 minus 17 or 733 mm. Then. 
if it were required to find the true volume at standard 
pressure, the following substitution would be made in 
the formula, YP = V'P' 

900 x (750 -17) =Y'x760 

The following table gives the aqueous tension for a short 
range of ordinary room temperatures. 



Temperature 


Aq. Tension 


Temperature 


Aq. Tension 


16° C. 


13.51 mm. 


21° C. 


18.19 mm. 


17 


11.12 


22 


19.66 


18 


15.36 


23 


20.88 


19 


16.35 


24 


22.18 


20 


17.39 


25 


23.55 



8. Application of these Laws. — The gas in most cities 
is furnished by some company which is required by or- 
dinance to maintain a certain pressure, say 6 or 8 inches, 
water pressure. If instead of doing this the company 
allow the pressure to drop to 4 or 2 inches or any lower 
pressure than that specified, it is. according to Boyle's 
law, furnishing the consumer an expanded gas : therefore, 
while the meter registers the. larger amount the consum- 
er only has the value contained in the real volume. It 
should be stated, however, that as the 6 or 8 inches re- 
quired is necessarily the pressure in addition to one at- 
mosphere or 30 water feet, a drop of 4 inches is not rel- 
atively large. Nevertheless, consumers should be fur- 
nished gas by the number of heat units contained and 
not by volume. The aeronaut must observe these gas 
laws in filling his balloon. Too great initial pressure, 
when he has ascended into a rarer atmosphere, and 
bright sunlight, may result in such increased pressure 
through expansion from the heat of the sun as to burst 
the balloon. On the other hand, too low initial pressure, 



GASES AND SOME GAS LAWS 93 

when night comes, with the great drop of temperature in 
the upper air may cause such contraction of volume that 
the buoyancy of the balloon will no longer support the 
attendant weight. 

9. Some Deductions. — Cooling or heating a given vol- 
ume of gas does not change its weight. Compressing, 
or the reverse, likewise, has no effect upon the weight; 
therefore, obviously by any of these changes we have 
not affected the real quantity of the gas. At sea level, 
the pressure of the air per square inch of surface is about 
15 pounds. Now it is possible by modern appliances to 
obtain pressures approximating 150,000 pounds to the 
square inch. To some gases, such pressures as these may 
be applied and they are still gases unless the tempera- 
ture is also greatly decreased: according to Boyle's 
law the volume has been decreased to one ten-thousandth 
part of what it was originally. In other words, the par- 
ticles constituting the gas have been moved closer to- 
gether, so that now they are only one ten-thousandth 
part as far from each other as they were at the begin- 
ning. Under moderate pressures, as we have seen, all 
gases behave alike ; hence, there can be only one deduc- 
tion and that is that all gases are composed of particles 
not touching each other ; really, of particles at relatively 
great distances from each other. As all liquids may 
likewise be compressed, though but slightly and irreg- 
ularly, their particles also must not be contiguous. This 
may be shown to be true by a simple experiment. If 
a liter cylinder be half filled with alcohol and then a 
like amount of water cautiously introduced beneath the 
alcohol by means of a pipette, at first there will be 1,000 
c.c. of the two unmixed liquids (Fig. 24). Now, if by a 
stirring rod they are thoroughly mixed, the volume will 
be found to have decreased about 10 per cent. Like- 



94 



APPLIED CHEMISTRY 



wise, consider able quantities of various solids like salt, 
or sugar or alum may be dissolved in a given volume of 
water without increasing the volume to any great ex- 
tent. It is like pouring a pint of sand upon a quart of 
coarse shot. By adding the sand cautiously with fre- 
quent shaking, the sand may be largely introduced into 
the bottle of shot. About 500 liters of hydrogen chlo- 
ride gas may be passed into a liter of ice water with 
comparatively little increase in volume, and of ammonia, 



Before mixinf A-fter mixinS 




Fig. 24. — Contraction of volume on mixing two liquids. 



more than 1,000 may be thus introduced. Experiments 
with solids many years ago showed that they were po- 
rous. Metal globes filled with water were subjected to 
pressure and were flattened. The liquid was forced 
through the metal and, appearing as drops upon the out- 
side, showed that there were spaces between the particles 
of the solid through which the water particles could 
pass. Another experiment made some years ago in Lon- 
don proves not only the same thing, but that the par- 



GASES AND SOME GAS LAWS 95 

tides of a solid are even free to move about from one 
place to another. Some cylinders of lead were placed 
npon sheets of gold and allowed to remain thus for four 
years. Analyses were then made of the lower end of 
the lead cylinders and the gold was found to have pene- 
trated them to a distance of 8 mm. 

10. Molecular Theory. — The foregoing and many other 
experiments have led scientists to believe as conclusive 
that matter is not continuous, but made up of minute 
particles not touching each other. To these they have 
given the name of molecules. They are the smallest divi- 
sion of matter possible without destroying the identity 
of the substance. Thus a molecule of water or of salt 
would possess all the essential characteristics of the larger 
mass of water or salt. In solids these molecules are close 
together; in liquids farther apart, and in gases at rela- 
tively very great distances. To illustrate: In a gas un- 
der ordinary room conditions, the individual molecules 
are relatively farther apart than is the moon from the 
earth, when diameters are considered. The diameter of 
the earth is about 8,000 miles, so that the distance of the 
moon is only about 30 times the diameter of the earth. 
Many gases may be compressed thirtyf old and still remain 
gases, showing that their molecules are still far apart. A 
gas which may be compressed by ten thousand atmos- 
pheres would have its molecules brought ten thousand 
times nearer together than they were ; ten thousand times 
the diameter of the earth would approach in distance that 
of the sun from the earth. This gives some idea of the 
real distance of the molecules from each other. A bottle 
full of hydrogen, as we say, is really a bottle with com- 
paratively few particles of the gas at relatively great 
distances from each other. It is difficult for the human 
mind to form any conception of the infinitesimal size of 



9Q APPLIED CHEMISTRY 

a molecule. Someone has said that if a buckshot were mag- 
nified to the size of the earth and the composing mole- 
cules likewise were magnified, they would then be .some- 
thing like the size of the buckshot. Lord Kelvin, the 
great English scientist, has shown that in solids, the dis- 
tance from the center of one molecule to the center of 
the next is not less than one five-hundred-millionth of an 
inch. So if they were actually touching, their diameters 
would be one five-hundred-millionth of an inch. If their 
distances apart equal the diameter of the molecule, then 
their diameters would be one half as great or one billionth 
of an inch. To count the number possible of lying upon 
a line 1 inch long, at the rate of one per second, would 
require nearly 39 years of 360 days each, ten hours 
per day. Automobiles, equal in number, with a wheel-base 
of 120 inches spaced 10 feet apart would form a proces- 
sion reaching a little more than seventy-five times around 
the earth. 

11. Molecules Not at Rest. — At several times in pre- 
ceding chapters it has been necessary to refer to the fact 
that the particles of gases or liquids are not at rest. The 
experiment of Roberts-Austin of the gold leaf under 
the lead cylinders shows the same for solids. Molecules 
are not like dust particles in the air. These soon settle 
when the existing cause is removed, but not so with mole- 
cules. According to Boyle's law, when the pressure is 
removed from gases, they tend to expand indefinitely, 
so that a pint of any gas opened into a vacuum, no mat- 
ter how large, would be quickly distributed throughout 
the entire space. The passage of a gas throughout the 
space occupied by another or of one liquid through an- 
other has been spoken of as diffusion, and can be ex- 
plained only on the assumption that molecules possess the 
inherent power of motion and that they are continuously 



GASES AND SOME GAS LAWS 97 

in motion. This is known as the kinetic theory of gases. 

12. Gas Pressure, Result of This Motion. — By methods 
not necessary to be discussed here, it has been learned 
that the average velocity with which these gas molecules 
are moving is very considerable. With the lightest 
gases such as hydrogen, it is several miles per second. 
Naturally, therefore, the numerous successive impacts 
upon the wall of any containing vessel must produce a 
pressure. Such is the cause of the pressure exerted by 
any gas upon the inside of the containing vessel and 
is simply its resistance to being compressed. It is not 
the same as the air pressure upon a surface at any par- 
ticular altitude, for that is merely the weight of the 
column of air supported at that point. In discussing 
hydrates in Chapter II, it will be remembered that a 
manometer tube was mentioned as being used to show 
the pressure of the water vapor at different tempera- 
tures. It is simply the impacts of the molecules of va- 
por upon the surface of the mercury that push it up 
into the bent tube. Similarly, when w T e pump air into 
an automobile tire and the pressure gauge registers an 
increase from 4-0 to 80 pounds, we have simply doubled 
the quantity of air in the tire so that the number of im- 
pacts per second has been doubled. 

13. The Atomic Theory. — John Dalton, a scientist who 
died in 1844, showed conclusively that while the as- 
sumption of the molecular structure of matter satisfies 
most of the needs of physical phenomena, it does not 
explain many things in chemistry. He proposed what 
is now known as the atomic theory. The most important 
features of this theory are, first, that molecules are cap- 
able of division into still smaller particles, which he 
called atoms. The word means not able to be divided. 
and up to comparatively recent years the atom has been 



98 APPLIED CHEMISTRY 

regarded as the smallest possible division of matter. It is 
usually defined as the smallest particle of matter capable 
of entering into a chemical reaction. Second, it is as- 




Fig. 25. — Dalton, who proposed the atomic theory of matter. 

sumed by this theory that the atoms of each particular 
element have a definite and fixed weight. Hence, when 
they enter into combination, one or more of these defi- 
nite weights must be used. Third, the weight of an atom 



GASES AND SOME GAS LAWS 99 

of each element is different from that of every other 
element; fourth, chemical action takes place between 
atoms and not between larger masses. Accordingly, to 
use a somewhat unscientific illustration, matter is tied up 
by nature in small packages or bundles, and when these 
are used together in chemical reactions it becomes neces- 
sary to use one, two or more of the packages. 

14. The Corpuscular Theory. — As stated just above, 
the word atom means unable to be divided. Recently, 
however, it has been found that certain substances, ra- 
dium for example, are able to give off particles with a 
velocity nearly the same as that of light and with a mass 
about one-thousandth part that of the hydrogen atom. 
These particles are called electrons or corpuscles, and are 
found to carry a negative charge of electricity. Further, 
electrons, no matter what their origin, all seem to be of 
the same mass. Prof. J. J. Thompson suggests that just 
as the molecules of a gas are at great distances from each 
other, so are these electrons in the atom, and he com- 
pares them to a thousand dots (.) scattered throughout 
a church building. The work of Thompson and of other 
experimenters seems to admit of no doubt as to the truth 
of the theory, yet it in no way lessens the value or de- 
stroys the probability of the truth of the atomic theory. 
Chemical action is between or among atoms, and the ex- 
istence of electrons simply aids in explaining many phe- 
nomena observed which otherwise is not possible. 

15. Atomic Weights. — It was stated above that Dal- 
ton's atomic theory assumes that the atoms of each ele- 
ment have a particular and definite weight. Naturally, 
it will be understood that to weigh anything so small as 
an atom is impossible. Hence, atomic weights are merely 
relative weights. As hydrogen is the lightest of all sub- 
stances, it would be presumed that its atom would be 



100 APPLIED CHEMISTRY 

used as a standard for measuring others. This was at 
first done and the term microcritli was applied to the unit. 
On this basis the weight of the oxygen atom is approxi- 
mately 16, more accurately, 15.998. It was found, fur- 
ther, that if the hydrogen atom was assumed to have a 
weight of one microcritli, the atomic weights of a large 
number of other elements differ considerably from whole 
numbers. On the other hand, if oxygen is assumed as 
weighing exactly 16 microcriths, which will give hydro- 
gen a weight of 1.008, a very considerable number of the 
other elements will have atomic weights of either whole 
numbers or closely approaching these. On account of the 
advantage which this affords in accurate chemical calcu- 
lations, it is regarded as preferable. Tables of atomic 
weights are, therefore, usually given on the basis of the 
oxygen atom having a mass of 16 microcriths. To define 
atomic weight, therefore, we would say that it is the weight 
in microcriths of an atom of any element as compared 
with the oxygen atom whose mass is 16 microcriths, or with 
hydrogen, 1.008 microcriths. Thus when we say sulphur 
has an atomic weight of 32, we mean in the form of va- 
por it is twice as heavy as oxygen or nearly 32 times as 
heavy as hydrogen. (See page 441.) 

16. Molecular Weights. — The molecular weight of a 
substance is the sum of the weights of all the atoms 
found in a molecule of that particular substance. It will 
be shown later that a molecule of water contains two 
atoms of hydrogen and 1 of oxygen. Adding the weights 
of two atoms of hydrogen and 1 of oxygen, gives for water 
a molecule weight of 18. Thus, knowing the composition 
of the molecule of any substance, we may determine its 
molecular weight. 

17. Avogadro's Hypothesis. — The great Italian phys- 
icist in 1811 formulated the hypothesis which bears 



GASES AND SOME GAS LAWS 



101 



his name. It is, Equal volumes of all gases under the same 
pressure and temperature, contain the same number of 
molecules. To illustrate, this simply means that if 1 c.c. 
of hydrogen contain a thousand molecules, one of oxygen 
or any other gas would contain the same. No absolute ex- 
perimental proof of its truth has been furnished, but 
similar changes of volume for all gases under varying 
temperatures and pressure, as well as many other ob- 




Fig. 26. — A simple eudiometer connected to induction coil, marked I. 



served facts, are strong presumptive evidences of its 
truth. 

18. Numbers of Atoms in a Molecule. — Assuming the 
truth of the hypothesis just given, it is possible to as- 
certain the number of atoms in a molecule of the various 
gaseous elements or of those which may be vaporized. 
For example, it has been found that water consists of 
two volumes of hydrogen to one of oxygen. If the con- 
verse of the experiment described in Chapter II be car- 



102 APPLIED CHEMISTRY 

ried out with an apparatus called a eudiometer, shown 
in Fig. 26, and correction be made for temperature, this 
fact is observed : 

2 volumes of hydrogen exploded with 1 of oxygen produce 2 vol- 
umes of steam, or putting it more concretely, 
20 c.c. hydrogen with 10 c.c. oxygen produce 20 c.c. steam. 

The experiment shows that the 30 c.c. of mixed gases 
when combined yield only 20 c.c. of the vapor, there 
being a condensation of one-third. Applying Avoga- 
dro's hypothesis, supposing there are 20 thousand mole- 
cules in the 20 c.c. of hydrogen, and substituting we 
should have — 

20 thousand mol. hydrogen with 10 thousand mol. O. produce 20 

thousand mol. steam ; 

or, 

2 mol. hydrogen + 1 mol. oxygen give 2 mol. steam. 

Now it must be admitted as true that each molecule of 
steam contains some oxygen ; hence, as there are 2 mole- 
cules of steam produced for every molecule of oxygen, 
the oxygen molecule must have been divided into two 
parts. Using the same apparatus and substituting chlo- 
rine for oxygen, but using equal volumes of each gas, 
the experiment may be repeated, with these results: 

20 c.c. hydrogen + 20 c.c. chlorine give 40 c.c. hydrogen chloride. 

Here it will be noticed that although chemical change 
has taken place the volume has not changed, the new 
substance having the same as the combined volume of 
the mixed gases. Applying Avogadro's hypothesis as 
before, 

2 mol. hydrogen + 2 mol. chlorine give 1 mol. hydrogen chloride. 

Now since the number of hydrogen chloride molecules 
is double that of the hydrogen molecules, each one of 



GASES AND SOME GAS LAWS 103 

the latter must have been broken into at least two portions. 
Likewise has the chlorine molecule. Since no cases have 
ever been observed in which the molecules of these gases 
are broken into more than two parts, it is assumed that 
a smaller division is impossible chemically and these 
particles are atoms. With the exception of ozone, which 
has been stated as being a peculiar form of oxygen, 
with three atoms to the molecule, all the common ele- 
mentary gases, like hydrogen and chlorine, have two 
atoms to the molecule and are said to be diatomic. Argon, 
helium, and the other rare gases, belonging to the same 
family, are monatomic. Mercury and some other metals 
are likewise monatomic, while phosphorus and arsenic are 
tetratomic. 

19. Gay-Lussac's Law. — In all the experiments out- 
lined just above where one gas combined with another, 
it will be noticed that the volumes always bore some 
simple relation to each other. When weights are con- 
sidered, this is often not true. For example, in common 
salt by weight chlorine unites with sodium in the pro- 
portion of about 35.5 to 23. In volumes it will be seen 
that exactly two of hydrogen combine with one of oxy- 
gen to form water ; one of hydrogen combines with one of 
chlorine to produce hydrogen chloride, and three of hy- 
drogen with one of nitrogen to form ammonia. This has 
been discovered to be a general truth and has been form- 
ulated in what is known as Gay-Lussac's law. It is usu- 
ally stated thus: The volumes of gases when uniting with 
each other chemically and of the gaseous products formed 
by the union may always be expressed in small whole 
numbers. This law will be further illustrated in the fol- 
lowing chapter in some problems of combiistion. 

20. Determination of Molecular Weights. — It lias boon 
found by experiment that a liter of hydrogen weighs 



104 APPLIED CHEMISTRY 

.0898 grams, and one of oxygen 1.429 ; or, in larger 
amounts, 22.4 liters of hydrogen weigh 2 grams and 
the same volume of oxygen, 32 grams. According to 
Avogadro's hypothesis, since there are the same num- 
ber of molecules of each gas in the 22.4 liters, the rela- 
tive weight of the two must be the relative weight of 
the two molecules. It may be said, in fact, that 22.4 liters 
of any gas will always weigh approximately as many 
grams as there are microcriths in the molecular weight 
of that gas. It has been stated above that hydrogen and 
oxygen are both diatomic gases ; hence, since their atomic 
weights are 1 to 16 respectively, their molecular weights 
would be 2 and 32 respectively which correspond to the 
weights in grams given above for 22.4 liters. Likewise, 
the molecular weight of carbon monoxide is 28, and 22.4 
liters weigh approximately 28 grams. This fact may be 
used to determine the molecular weight of various gases. 
For example, 22.4 liters of carbon dioxide weigh approx- 
imately 44 grams; hence, the molecular weight of this 
gas would be 44. 

21. Gram Molecular Weight. — The molecular weight 
of any substance, stated in grams, is called its gram mo- 
lecular weight. Thus the molecular weight of water is 
18 ; of cane sugar, 342 ; hence, 18 grams and 342 grams 
would be respectively gram molecular weights of these 
two substances. Sometimes such a weight is spoken of 
as a mol or a molar weight. If a gram molecular weight 
of various gases be measured under standard temperature 
and pressure, allowing for slight variations which admit 
of explanation, the volume is always approximately 22.4 
liters. Thus, 

Hydrogen, 2 grams occupy 22.4 liters 
Oxygen, 32 grams occupy 22.4 liters 
Nitrogen, 28 grams occupy 22.4 liters 
Carbon Dioxide, 44 grams occupy 22.4 liters 



GASES AND SOME GAS LAWS 105 

Conversely, therefore, if we determine the weight of 22.4 
liters of any gas we have a means of knowing approxi- 
mately its molecular weight. This method often serves 
in checking up other methods of finding molecular weights 
and in this way is of great value. 

Exercises for Review 

1. Name the three states of matter and the two forces which 
govern them. 

2. State Charles' law. Illustrate. What is the absolute zero 
point? How did it come to be adopted? 

3. State Boyle's law. What is meant by standard pressure and 
temperature ? 

4. What is the formula for correcting volumes when both tem- 
perature and pressure change? 

5. What is meant by aqueous tension? Would it be used when 
a gas is collected over mercury? Explain. 

6. What can be said about the contiguity of matter? Why must 
this conclusion be reached? 

7. Give some experimental proof that matter is not continuous. 

8. What is the molecular theory? A molecule? Give some idea 
of the size of a molecule ; of the distance they are apart in gases. 

9. What proofs can you offer that molecules are not at rest? 

10. What gives the pressure on the inside of a tire on a motor 
car? If you double the quantity of air already in a tire what ef- 
fect upon the pressure? Why? 

11. Give the four main assumptions of the atomic theory. What 
is an atom? 

12. What is an electron? What can you say of its mass? Does 
this theory destroy the truth of the atomic? Why? 

13. What is meant by the atomic weight of an element? Illus- 
trate. What is a microcrith? 

14. State Avogadro's hypothesis. Of what use is it? 

15. What is a monatomic molecule? A diatomic? Name some. 

16. Give one method of determining experimentally the molecu- 
lar weight of a gas. 



CHAPTER VII 

SYMBOLS AND FORMULAS 
Outline — 

The Origin of Symbols 
Present Use of Symbols 
Formulas 

(a) Empirical 

(Z>) Structural 
Eadicals 
Equations 

1. Origin of Symbols. — The use of symbols began with 
the alchemists who sought thereby to render unintelli- 
gible the notation of their attempts at making gold 
from the baser elements. Modern chemists have found 
it necessary in mathematical calculations and in vari- 
ous other ways to use short methods of representing 
chemical compounds and the reactions taking place. 
Moreover, chemical symbols as now used are intelligible 
to all chemists the world oi^er, so that out of a plan 
adopted to keep secret the work done has come a uni- 
versal language read by all chemists. 

2. What Are Symbols? — A symbol is a letter or letters 
used to represent a single atom of an element. L T sually 
it is the initial letter, but as this is the same for a number 
of elements, the initial letter is often followed by some 
other distinctive one of the word. It must be noted that 
the initial letter is always capitalized, while the second, 
if another be used, is not. Thus C is the symbol for 
carbon ; Ca for calcium ; Cd for cadmium ; Co for cobalt. 
Several of the elements receive their symbols from the 
Latin or some other foreign language; thus, K is for 

106 



SYMBOLS AND FORMULAS 107 

potassium, Kalium; Na for sodium, Natrium; Ag, silver, 
Argentum; Hg for Mercury, Hydrargyrum. 

3. Formulas. — A formula is a combination of symbols 
representing a molecule of a substance, usually that of a 
compound. In its broadest sense it may represent the 
molecule of an element. Thus, HC1 is the formula for 
hydrogen chloride, while HH, usually written H 2 is the 
formula for a molecule of hydrogen. To represent the 
formula of a compound naturally the number of atoms 
of each element contained must be shown. If there be 
more than one of any of them, that fact is indicated by 
a small figure written at the right and slightly below the 
symbol to be multiplied. Thus, water is H 2 0, showing 
two atoms of hydrogen to one of oxygen per molecule: 
likewise sulphuric acid has the formula, Ii 2 S0 4 ; sugar, 
C 12 H 22 11 . Sometimes a certain group or combination of 
symbols will be contained more than once in the com- 
pound; in such cases the group is usually enclosed in 
parentheses and the number of times it is contained ex- 
pressed by a subfigure. Thus, aluminum carbonate is Al 2 
(C0 3 ) 3 in which the group C0 3 occurs three times. It 
might be written C 3 9 , but for reasons which will ap- 
pear later the method first given is usually followed. If 
it is desired to represent more than a molecule of a sub- 
stance, the proper figure is placed before the formula as 
a coefficient. Thus, 5K 2 C0 3 indicates five molecules of 
potassium carbonate and the coefficient multiplies each 
symbol in the formula. That is, in 5K^ 2 C0 3 there are not 
only ten atoms of potassium, but five of carbon and fifteen 
of oxygen. Sal soda has the formula, Na 2 C0 3 . 10H 2 O. 
Written thus it is typical of the method used for all hy- 
drates. The number of molecules of water entering into 
the compound is indicated by the coefficient of the water. 
Written thus, that the compound is a hydrate, is indicated 



108 APPLIED CHEMISTRY 

at once, as is also the fact that the combination is some- 
what of a molecular or loose one. 

-i. Structural Formulas. — Often it is very desirable 
to show how the atoms are arranged in the molecule. 
Especially is this true in the case of many compounds of 
carbon, in which two or more may have the same per- 
centage composition and same molecular weight, but 
very different properties. Thus. C 2 H 6 is the empirical 
formula for more than one compound in which there are 
two atoms of carbon, six of hydrogen and one of oxygen 
per molecule, but the formula shows nothing more. Ob- 
viously, if written C 2 H 5 OH or (CH 3 ) 2 0. the molecular 
weights are the same, but the first indicates an alcohol 
and the second an ether. To the chemist, written thus, 
they indicate the manner of arrangement of the atoms in 
the molecule. This is shown more fully thus ; 

H H 
H-C-C-O-H. ethyl alcohol. 

ii h 

H H 

I I 
H-C-O-C-H, methvl ether. 
I i 
H H 

Such formulas as these are called structural or some- 
times graphic, and in very complex compounds are of 
the greatest help in understanding the relations existing. 
5. Radicals. — In many compounds certain groups of 
elements will be found, which behave as if they were 
single elements. Thus in sulphuric acid and in all the 
sulphates there occurs the group. - S0 4 . This constitutes 
the negative portion of the compound and in case of 
electrolysis appears at the positive electrode. It can- 



SYMBOLS AND FORMULAS 109 

not be separated out or isolated, and in the electrolytic 
apparatus it immediately combines with the anode if 
that be possible; if not, it combines with hydrogen from 
the water present and forms a molecule of sulphuric 
acid. Looking at the formulas, K 2 S0 4 , CuS0 4 , 
A1 2 (S0 4 ) 3 , K 2 A1 2 (S0 4 ) 4 , we see the same combination of 
elements. All such groups are called radicals. Ordi- 
narily the term indicates a group of atoms forming a 
part of a compound but unable to exist alone. There 
is only one common electropositive radical, ammonium, 
NH 4 - ; it is found in all ammonium compounds. Thus am- 
monium chloride, NH 4 C1, ammonium sulphate (NH 4 ) 2 S0 4 . 
The other more common radicals are - N0 3 seen in nitric 
acid and all nitrates, - C0 3 in the carbonates, - P0 4 in 
phosphates, - C10 3 in chlorates, - HO in hydroxides. 

6. Equations. — Chemical changes or reactions have 
been classified as being mainly of three kinds. It is 
customary among chemists to show what takes place 
in a chemical change by an equation. The left hand side 
contains the formulas of the substances used and the 
right hand side, the products formed, with the sign — > 
between, which is read yields or produces. Going back 
to the experiment of heating mercuric oxide, we find that, 

Mercuric oxide, heated, yields oxygen and mercury. 
For the sake of brevity this is written, 

HgO (heated) -» Hg + 

or better, 

2HgO(heated) -> 2Hg + 2 . 

It was stated in the preceding chapter that the oxygen 
molecule contains two atoms. It is known that all sub- 
stances exist as aggregations of molecules and not of 
atoms. The second equation just above shows the oxy- 



110 APPLIED CHEMISTRY 

gen in the molecular form as it would exist after it has 
been liberated from the compound, hence is the better 
form. 

Again, water electrolyzed, gives hydrogen, two parts 
and oxygen, one. More briefly, but indicating the same 
thing, 

2H 2 -> 2H 2 + 2 

Equations are not something merely abstract as equations 
in algebra, or merely theoretical. Every equation must be 
verified by actual experiment, otherwise it has no value. 
For example, we prepared hydrogen by allowing sodium 
to react with water. Algebraically we might write the 
equation, 

2Na + H 2 -> Na 2 + H 2 or 
2Na + 2H 2 -> 2XaHO + H 2 . 

Only by experiment can we know which is correct. The 
first of the two equations shows sodium oxide formed; 
the second, sodium hydroxide. "Which is correct ? Chem- 
ical tests show that, performed as the experiment was, 
sodium hydroxide is present ; hence, the equation must 
be written to show that fact. We prepared oxygen by 
heating potassium chlorate, KC10 3 . Theoretically, all or 
part of the oxygen might be displaced by heating the com- 
pound, just as was the case when sodium reacted, as 
above, with water in producing hydrogen. Testing the 
residue shows that potassium chloride is present, and our 
equation must be written to indicate the fact, thus, 

2KC10 3 -» 2KC1 + 30 2 . 

In like manner all equations are determined by experi- 
ment and merely state in brief form what was learned 
thereby. 



SYMBOLS AND FORMULAS 111 

Exercises for Review 

1. What was the origin of symbols? Give the purpose of a sym- 
bol now. 

2. Define a symbol. 

3. Of what do symbols consist and how written? Illustrate. 

4. Give several derived from the Latin or Greek. 

5. What is a formula and what does it represent in its broad- 
est sense? 

6. What effect has a coefficient before a formula? Illustrate. 
How is it different from the coefficient as used in algebra? 

7. What is a structural formula? Of what advantage? 

8. What is a radical? Give five. How are they different from 
compounds? 

9. What is the purpose of an equation? What do they show? 

10. Which is the better form, and why : 2K + 2H,0 — > H 2 + 2KHO, 
or, K + H 2 -» H + KHO? 

11. How do chemists know whether an equation is correct? 

12. Is this equation true: CuS0 4 + 2KHO -> Cu(HO) 2 + K 2 S0 4 ? 
How can you find out? 



CHAPTER VIII 

SOME CHEMICAL PROBLEMS 

Outline — 

Practical Value of the Equation 

Problems in Manufacturing Industries 
Percentage Composition of Compounds 
Problems in Combustion 
Liter Weights of Gases 
Determination of Formulas 

1. Value of Equations. — Almost every manufacturing 
industry involves more or less chemistry. In baking 
powders, of the three ingredients most often used, two 
of them must be exactly proportioned, otherwise the 
food in which they are used will be valueless. The 
chemical change occurring when such chemicals are put 
together is first determined by experiment in the labora- 
tory; this is then expressed by an equation, and from 
this without repeating the experiment the quantities 
needed may be calculated by any one at any time. To 
illustrate with a case somewhat simpler than that of 
baking powder, we have learned that 

2KC10 3 -> 2KCl-30 2 . 

This equation shows that two molecular weights of po- 
tassium chlorate produce three molecular weights of 
oxygen. Calculating these weights from the table of 
atomic weights given on p. 441, we find that 245 parts of 
potassium chlorate yield 96 of oxygen. Suppose a man- 
ufacturer needs to know how much oxygen he can obtain 
from 1,000 grams of potassium chlorate. Knowing from 

112 



SOME CHEMICAL PROBLEMS H3 

the equation that 245 grams of the chlorate will 
produce 96 of oxygen 1,000 will produce x grams, or 

245 : 96 : : 1,000 : x, 

from which x may be easily calculated. Or, putting it in 
another form, the oxygen obtained is seen to be 96/245 
of the weight. of the chlorate used. The oxygen obtained, 
therefore, would be 

96/245 of 1,000 ^ 96X1 ' 000 
245 

Manufacturers of oxygen for use in the oxyhydrogen 
blowpipe or for other purposes furnish it in gaseous form, 
which might sometimes be given in volume and not 
weight as above. Knowing the weight of a liter of oxy- 
gen, 1.43 gram, which may be obtained by multiplying 
the weight of a liter of hydrogen by the density of oxy- 
gen, if we divide the weight obtained above by the weight 
of a liter of oxygen we shall have the volume. It may also 
be obtained another way, which is often easier. It has 
already been stated that a gram molecular weight of oxy- 
gen as of any other gas is 22.4 liters. By looking at the 
equation, 

2KC10 3 -^2KCl + 30 2 , 

we see that two molecular weights of potassium chlorate 
produce three molecular weights of oxygen. But 3 gram 
molecular weights of oxygen would be, in volume, three 
times 22.4 liters. That is, 245 grams of potassium chlo- 
rate would produce 3 x 22.4 liters of oxygen, or 67.2 
liters. Hence, 1,000 grams of potassium chlorate would 
yield 

1,000 

— x 67.21. 

245 

This would be the volume under standard conditions of 



114 APPLIED CHEMISTRY 

temperature and pressure. If the gas is to be delivered 
under five atmospheres' pressure, according to Boyle's 
law. five volumes of the uncompressed gas must be pre- 
pared for every one of that to be delivered. 

2. To Find Percentage Composition. — Knowing the 
formula, the method is very simple. Suppose it is de- 
sired to know the amount of water contained in Epsom 
salt, MgS0 4 .7H 2 (X Ascertaining the atomic weights 
from the table, p. 441. we have 

24 + 32 + 64+ (7x18) =246. 

The weight of the seven molecules of water is 126. It is. 
therefore. 126 246 of the whole compound, or 51.2 per 
cent. 

3. Some Combustion Problems. — Ordinary combustion 
has been defined as rapid oxidation. It is often desir- 
able to know the character and quantity of products 
formed as well as the amount of air needed for per- 
fect combustion. Natural gas consists mainly of what 
is known as marsh gas, CH 4 . AVhen it burns the follow- 
ing equation illustrates the change taking place, 

CH 4 + 20 2 ->C0 2 + 2H 2 0. 

This shows that one volume of marsh gas requires two 
volumes of oxygen and produces one of carbon dioxide 
and two of vapor. Applying Avogadro's hypothesis, 
any problems involving volumes may be read off at once 
from the equation. Suppose 1.000 cubic feet of marsh 
gas are burned: from the equation we can see that twice 
as much oxygen would be needed and there would be 
produced the same volume of carbon dioxide and twice 
the volume of water vapor. As air is only about one- 
fifth oxygen, to burn this volume of gas would require 



SOME CHEMICAL PROBLEMS 115 

10,000 cubic feet of air. Acetylene is a gas producing 
great heat when properly burned and often used in blow 
pipe work for welding, 

2C 2 H 2 + 50 2 -> 4C0 2 + 2H 2 0. 

The equation indicates that two volumes of acetylene re- 
quire five of oxj^gen and yield four of carbon dioxide 
and two of vapor. From this it is seen at once that 1,000 
cubic feet of the gas would need two and a half times 
as much oxygen or 2,500 cubic feet, and would produce 
2,000 cubic feet of carbon dioxide and 1,000 of vapor. 
When rooms are warmed by an open gas heater or by an 
oil stove, by which the necessary oxygen is taken directly 
from the room and the products left in the room, it is 
seen how rapidly the air is being vitiated. The water pro- 
duced in such cases is often sufficient to loosen the paper 
upon the walls, and even the parts of furniture glued 
together. It must be remembered that the air being used 
is more than five times the volume of the oxygen shown 
in the equation. 

4. To Find the Weight of a Liter of Any Gas. — It is 

not necessary for the student to commit to memory many 
figures. But the weight of a liter of hydrogen should 
be remembered, for by means of it the weight of a 
liter of other gases may readily be calculated. It is nec- 
essary first to determine the vapor density of the gas, 
that is, its density compared to hydrogen. Obviously, 
from Avogadro's hypothesis, if we divide the molecular 
weight of any gas by the molecular weight of hydrogen, 
we shall have the density of the gas compared to hydro- 
gen. The molecular weight of hydrogen is 2, hence divid- 
ing the molecular weight of any gas by 2 gives its vapor 
density. Then, knowing the weight of a liter of hydrogen, 
if we multiply this by the density we shall have the 



116 APPLIED CHEMISTRY 

weight of a liter of the gas in question. To illustrate: 
Take carbon dioxide, C0 2 . It has a molecular weight of 
44; its vapor density would, therefore, be 22: multiply- 
ing the weight of a liter of hydrogen, .0898, by 22 gives 
1.9756 as the weight of a liter of carbon dioxide. 

5. Determination of Formulas. — Knowing by experi- 
ment the percentage composition of a substance, and 
the atomic weights of the elements contained, it is possi- 
ble to determine the empirical formula. Thus, wood al- 
cohol contains 37% per cent of carbon, 12% per cent 
of hydrogen and 50 per cent of oxygen. Dividing 
these percentages by the atomic weight of each element, 
on the assumption that they are microcriths of weight 
and not percentages, we have 

37 - 5 =3.125 ^=12.5 4^=3.125. 



12 1 16 

Had the figures representing per cents really been mi- 
crocriths, as assumed, the quotients would have been 
the number of atoms of each element in the formula. 
While the assumption is not true, the mathematical re- 
lation obtained is true, that is, for every 3.125 atomic 
weights of carbon there would be 12.5 atomic weights 
of hydrogen and 3.125 of oxygen. If we divide through 
by the smallest of these weights we shall remove the 
fractional amounts and obtain as a result, carbon, 1; 
hydrogen, 4 and oxygen, 1. The formula, therefore, 
would be CH 4 0. To know whether this is correct the 
vapor density of the alcohol must be determined. Sup- 
pose by experiment this is found to be 16. We know 
from a previous statement that the molecular weight 
is double the density, hence the molecular weight of 
this compound would be 32. By adding the atomic 
weights represented in the formula obtained, CH 4 0, 



SOME CHEMICAL PROBLEMS 117 

we obtain 32, which agrees with the weight obtained by 
experiment ; hence is correct. Take another case. Anal- 
ysis of sulphuric acid shows it to contain hydrogen, 
2.04 per cent; sulphur, 32.65; oxygen, 65.30. Dividing 
these figures by the respective atomic weights we have as 
the quotients, 2.04, 1.02 and 4.08, which give the relative 
number of atomic weights contained in the molecule. 
Dividing by the smallest quotient, we have as a result, 
2, 1, 4 respectively, giving for the formula H 2 S0 4 . Again, 
acetylene has a percentage composition of carbon, 92.31, 
and hydrogen, 7.69 per cent. Dividing by the atomic 
weights we have as the quotients, 7.7 and 7.69. Dividing 
these results by 7.69 we have 1 and 1 respectively, which 
gives as the empirical formula for acetylene, CH. Is 
this correct? By experiment in the laboratory a liter 
of acetylene is found to weight 1.167 grams. As a liter of 
hydrogen weighs .0898 grams, acetylene is found to be 
thirteen times as heavy. The molecular weight, therefore, 
must be 2 x 13, or 26. If CH were the formula, its molec- 
ular weight would be only 13 ; hence, the empirical for- 
mula we obtained by calculation is just half the correct 
one ; in other words, it must be doubled, so that it becomes. 
C 2 H 2 . 

Exercises for Review 

1. Determine the weight of oxygen obtainable from 980 grams 
of potassium chlorate. What volume would the oxygen have? 

2. How much potassium chlorate would be needed to prepare 500 
liters of oxygen if under five atmospheres' pressure? 

3. What weight of hydrogen may be had from 260 grams of 
zinc by allowing it to react with sulphuric acid? Suppose hydro- 
chloric acid were used, what would be the weight of hydrogen? 

4. What weight of sulphuric acid would be needed to react with 
100 grams of magnesium in preparing hydrogen? What would be 
the volume of the hydrogen obtained? 

5. Calculate the per cent of sulphur in sulphuric acid. Also the 
per cent of oxygen. 



118 APPLIED CHEMISTRY 

6. What is the percentage of water in sal soda ; formula, 
XaXCUOHX) ? 

7. The gas ethylene has the formula, C 2 H 4 . If 1,000 liters of 
it are burned, what volume of carbon dioxide is produced and 
what of water vapor? 

S. Find the weight of a liter of oxygen; of carbon monoxide, 
CO; of ozone; of nitrogen monoxide, X,0; of arsenic vapor. 

9. The percentage composition of a certain alcohol is carbon, 
52.17, hydrogen, 13.0-1, and oxygen 34.78. Find the empirical 
formula. 

10. If the vapor density of nitric oxide is 15, is its formula 
NO or N 2 2 * 



CHAPTER IX 

THE HALOGENS 
Outline — 

Relation of the Halogens to Each Other 
Chlorine, its History 

(a) Preparation in Laboratory 

(b) Commercial Methods 

(c) Physical Characteristics 

(d) Chemical Characteristics 

(e) Uses 
Hydrogen Chloride 

Characteristics 
Hydrochloric Acid 

(a) Preparation 

(b) Characteristics 

(c) Uses 
Hydrofluoric Acid 

Uses 
Bromine 

(a) Occurrence 

(b) Preparation 

(c) Characteristics 

(d) Uses 
Iodine 

(a) Occurrence 

(b) Preparation 

(c) Characteristics 

(d) Uses 

1. General View. — There are four elements in the halo- 
gen group — fluorine, chlorine, bromine and iodine. They 
are called halogens, a word meaning salt producers, be- 
cause they all produce many compounds resembling com- 
mon salt; and from the similarity of their physical char- 
acteristics and their chemical behavior, must be re- 
garded as belonging to a single group of elements. Their 

119 



120 APPLIED CHEMISTRY 

densities compared to hydrogen are in the order given 
above, with atomic weights, respectively of, approxi- 
mately, 19, 35.5, 80 and 127. Their chemical activity 
is in the inverse order of their densities, that of iodine 
being the least. All have an irritating odor, although 
that of iodine is rather feeble when compared with the 
others. The two lightest are gases ; bromine is a liquid, 
the only liquid element except mercury, and iodine is 
a solid. 

2. Discovery of Chlorine. — It will be remembered that 
in 1773 Scheele prepared oxygen by heating manganese 
dioxide with sulphuric acid. The following year he ob- 
tained chlorine by treating manganese dioxide with 
hydrochloric acid, although he had no idea he had dis- 
covered a new element. Knowing that it was possible 
to obtain oxygen from manganese dioxide, he believed 
he had simply caused a union between the hydrochloric 
acid and the oxygen of the dioxide. And, in accordance 
with the phlogistic ideas of combustion, he named the 
gas dephlogistic cited marine acid air. At that time oxy- 
gen was often called dephlogisticated air ; hence, the 
name in modern chemical terms would be oxidized hydro- 
chloric acid gas, for marine acid was then what we now 
call hydrochloric. More than a quarter of a century 
passed away and chlorine was still unknown as an element 
until Sir Humphrey Davy gave it a careful study and 
so pronounced it. 

3. Preparation of Chlorine. — The usual laboratory 
method of preparing chlorine is the same as used by 
Scheele. (Fig. 27.) The accompanying figure shows one 
form of apparatus and the method of collecting. Being a 
gas much heavier than air it may be collected by downward 
displacement. As it is considerably soluble in water, the 
plan used in the case of hydrogen and oxygen is not satis- 



THE HALOGENS 



121 



factory, but may be employed if the water has a consid- 
erable amount of common salt dissolved in it. The man- 
ganese dioxide is placed in the flask, and when the col- 
lecting bottles are all ready the hydrochloric acid is added 
through the thistle tube and gentle heat applied as 
needed. 

4. Commercial Methods. — As chlorine is used so ex- 
tensively in various ways, several processes of obtaining 
it cheaply have been devised. Since common salt is 




Fig. 27. — Preparation of chlorine in the laboratory. 

abundant and not expensive, one of the plans widely 
adopted is that of separating its constituents, sodium 
and chlorine, by electrolysis. There are many difficul- 
ties in the way of carrying out the method successfully, 
but one type of machine is shown in Fig. 28. In the cen- 
ter compartment the bundle of carbon rods serves as 
the cathode, while a heavy carbon rod enters each of 
the two outer compartments, giving a double anode. 
The cathode dips into pure water, the anodes into sat- 



122 



APPLIED CHEMISTRY 



nrated salt solution; a thin layer of mercury covers the 
bottom of the apparatus aud fills two grooves into 
which the partitions dip, shown by the heavily shaded 
portion in the figure. Chlorine being an electronegative 
element is liberated at the anodes and is drawn off, 
dried, and compressed in tanks or drums. The sodium, 
electropositive, is repelled by the anodes, moves toward 
the cathode, meets the mercury and is dissolved by it. 
In the figure, E is an eccentric which rocks the tank 
continually. In this way the mercury containing the 
sodium is brought into contact with the water, where- 



W///////////^^ ^//////////M 




mmmmmmm 



Fig. 28. — Manufacture of chlorine. 



upon the sodium reacts with the water forming sodium 
hydroxide. The two reactions are 

2NaCl -» Cl 2 + 2Na, 
2Na + 2H 2 -> H 2 + 2NaHO. 

5. Physical Characteristics of Chlorine. — Chlorine is 
a greenish-yellow gas, about two and a half times as 
heavy as air, and of very irritating odor. It may be 
liquefied at -33.6° C. at atmospheric pressure and in 
this condition is a limpid, golden yellow fluid. It may 
be kept thus sealed hermetically in strong glass tubes. 
At about -102° C. it becomes a pale yellow solid, which 
upon further cooling changes to a pure white substance 
resembling snow. Upon melting it assumes the same 



THE HALOGENS 123 

yellow color again. It is soluble in water about two 
volumes to one.* 

6. Chemical Characteristics. — Chlorine is an exceed- 
ingly active element, possibly even more so than oxygen. 
Nearly all the metals, especially in a finely divided form 
or in thin sheets, ignite spontaneously in chlorine. So- 
dium must be heated before combustion takes place, 
but when this is done the action is vigorous with the 
formation of common salt. Turpentine, near its boil- 
ing point, on a strip of blotting paper, when lowered into 
a jar of chlorine, catches fire almost instantly, produc- 
ing an immense quantity of black smoke. Yellow phos- 
phorus in a deflagrating spoon in chlorine begins to burn 
almost immediately, and a jet of hydrogen, lighted in 
the air, continues to burn as well or better than before. 
From these experiments it is evident that combustion 
means more than the union of a substance with oxygen. 
Any two substances, combining with such rapidity as to 
produce heat and light, undergo combustion. Chlorine 
attacks the throat and bronchial tubes, causing great 
suffering for which there is no good antidote. A satu- 
rated solution of chlorine in water, if surrounded by ice, 
deposits yellow crystals of chlorine hydrate, having the 
composition C1.4H 2 0. A mixture of equal parts of hy- 
drogen and chlorine, if exposed to bright sunlight, ex- 
plodes with violence. The light from a burning magne- 
sium ribbon will bring about the same results. A solu- 
tion of chlorine in water, exposed to strong light, decom- 
poses, forming hydrochloric acid and setting free the oxy- 
gen. This is shown by a simple experiment illustrated by 
Fig. 29. The test tube is filled with chlorine water and 
inverted over an evaporating dish partly filled with the 
same solution. In a short time, bubbles of gas may be 
seen rising to the top of the tube; when the action has 



124 



APPLIED CHEMISTRY 



ceased the color will all have disappeared from the water. 
Chemical tests show that the gas is oxygen and that at 
the close the water contains hydrochloric acid. The final 
result is shown by the equation, 

2H 2 + 2C1 2 -> 2 + 4HCl. 

7. Uses of Chlorine. — Chlorine is used extensively for 
bleaching, especially cottons and linens. The cloth is 
drawn slowly through successive vats of bleaching pow- 
der solution and dilute hydrochloric acid. Thus the 
chlorine is set free and oxidizes the coloring matter. 
Much of the paper pulp used is bleached in the same 
way, and in the Middle West most of the large flour 




Fig. 29. — Effect of sunlight on chlorine water. 



mills employ liquid chlorine to bleach their products, 
to enable them to compete with other flours which by 
nature need no such bleaching. Practically all steam 
laundries now use chlorine to whiten the cotton and linen 
goods in order to please a critical public. Such frequent 
use of chlorine upon the fibers of the cloth greatly 
weakens them and hastens the end of their usefulness. 
Chlorine is frequently employed as a disinfectant; its 
use for the destruction of pathologic germs in city wa- 
ters has already been mentioned. Bleaching powder, 
a compound formed by the interaction of chlorine with 
lime is valuable in the sick-room; a small amount in a 



THE HALOGENS 125 

saucer, moistened with water, slowly gives off chlorine 
to the air. The quantity is so small as to be unnoticea- 
ble except close at hand, yet by diffusion throughout 
the room brings very valuable results. Chlorine is also 
used in the extraction of gold from its ores : for this 
purpose, bleaching powder, treated with hydrochloric 
acid is frequently employed, but in places remote from 
railway or other good means of transportation liquid 
chlorine put up in steel cylinders is used. Chlorine 
was the first of the poisonous gases used in the late war. 
Steel cylinders filled with the gas liquefied by great 
pressure were opened with nozzles towards the Allies 
with the wind blowing in that direction. Carried down 
hill by its own weight and aided by the wind the huge 
greenish-yellow billows caused the greatest suffering 
and thousands of deaths. Later the gas mask was de- 
vised to protect the wearer against such attacks. In 
the American mask all the air taken into the lungs was 
compelled to pass through a specially absorptive kind of 
charcoal made from the shells of nuts, or of charcoal 
mixed with an antichlor, a substance which combines with 
the chlorine. One of the best substances of this nature 
is what is known by photographers under the name of 
hypo or sodium thiosulphate. 

8. Hydrogen Chloride. — This compound has been 
known to chemists several hundred years, under the 
names, spirit of salt and marine acid air. It was so 
named because prepared from common salt, at that time 
derived mostly from the Mediterranean Sea. 

9. Physical Characteristics of Hydrogen Chloride. — It 
is a colorless gas of very irritating odor, and considera- 
bly heavier than air. It is very soluble in water ; a liter 
of water at 0° C. will absorb between 500 and 600 liters 



126 APPLIED CHEMISTRY 

of the gas. In other words, 600 liters are about the 
same as 600 quarts or three 50-gallon barrels, so that 
one quart of ice water will absorb about three barrels of 
hydrogen chloride. Blowing across the top of a tube or 
flask in which the gas is being evolved always shows 
heavy white fumes; this is because the moisture of the 
breath is absorbed and condensed by the gas. When a 
jet of hydrogen burns in a bottle of damp chlorine, or 
turpentine upon the blotting paper as previously de- 
scribed, a white cloud always appears, from the condensa- 
tion of the moisture by the hydrogen chloride formed. 

H 2 + Gl 2 -* 2HC1 
C 10 H 16 + 8C1 2 -* 16HC1 + IOC. 

These two equations represent the burning of hydrogen 
and of turpentine respectively in an atmosphere of chlo- 
rine. A liter of the hydrogen chloride weighs 1.64 grams. 
At - 83.7° C. it becomes a colorless liquid and at - 110° 
a solid. The liquid has no effect upon dry metals such 
as zinc and others, readily acted upon by the solution of 
the gas. 

10. Hydrochloric Acid. — When hydrogen chloride gas 
is allowed to pass into water the solution formed is 
called hydrochloric acid. The ordinary commercial va- 
riety, yellow in color, due to the presence of small quan- 
tities of iron chloride, is sold under the name, muriatic 
acid. It was formerly a by-product obtained in the man- 
ufacture of sodium carbonate, the first step of which in- 
volves the treatment of common salt with sulphuric acid. 
At temperatures such as those obtained in the laboratory 
with the bunsen burner, the following reaction takes 
place, 

NaCl + H 2 S0 4 -> HCl + NaHS0 4 . 

In the factories a much higher temperature is used with 



THE HALOGENS 127 

double the quantity of salt which results in a different 
reaction, thus, 

2NaCl + H 2 S0 4 -* 2HCl + Na 2 S0 4 . 

The gas thus obtained is conducted into towers filled with 
coke or some similar material, which is kept moist by wa- 
ter trickling over it. Owing to its great solubility the 
gas is all absorbed and when concentrated the solution is 
the acid of commerce. 

11. Characteristics of Hydrochloric Acid. — When 
pure it is a colorless solution. If a weak solution be 
boiled it becomes more and more concentrated until it 
reaches about 20 per cent of hydrogen chloride ; one 
stronger than this, if heated, gives off the gas faster 
than the water until it reaches a strength of about 20 
per cent, when it remains constant. Ordinary concen- 
trated hydrochloric acid contains about 36 per cent of 
hydrogen chloride and is strongly acid. Litmus paper 
is turned red as are various other vegetable colors or 
dyes; by such metals as magnesium, iron, zinc it is 
readily decomposed with the evolution of hydrogen. 
Thus, 

Zn + 2HC1 -h> H 2 + ZnCl 2 , 
Mg + 2HC1 -> H 2 + MgCl 2 . 

This is very different from the action of the liquid hy- 
drogen chloride. The two are not different in appearance, 
but the latter, as previously stated, does not affect dry 
metals; neither is it a conductor of electricity, whereas 
the acid is. 

12. Uses. — A century ago hydrogen chloride was a 
waste product of the Leblanc process of making soda 
crystals. Being heavier than air it settled down from 
the lofty towers built to carry it away, destroying veg- 
etable life and corroding tools and everything of a me- 



128 APPLIED CHEMISTRY 

tallic character. When conducted into streams it killed 
the fish and other aquatic animals, so that eventually 
most stringent laws were enacted against all such manu- 
facturers. Finally, by the aid of chemical research, 
valuable uses were suggested for it, and now it ranks 
among the most valuable of the acids. Every laboratory 
uses it abundantly; almost every manufacturing in- 
dustry employs it to a greater or less extent. In the stom- 
ach it is believed to be an essential of digestion. The 
fact that bones, very imperfectly masticated, are readily 
digested by various carnivorous animals is explained 
by the excessive amount of hydrochloric acid found 
in their stomach, which dissolves the mineral matter 
from the bones and leaves them about as soft as so 
much gelatine. Hydrochloric acid is used mixed with 
nitric acid, three parts of the former to one of the 
latter, in what is called aqua regia. The words mean 
royal ivater and were so employed for the reason that 
formerly this was the only known solvent for gold, the 
king of metals. The solution is effected by the chlorine 
which is set free thus, 

3HC1 + HN0 3 -> 2H 2 + 2C1 + N0C1. 

13. Hydrofluoric Acid. — The preparation of hydrogen 
fluoride is similar to that of the corresponding com- 
pound of chlorine. The cheapest natural compound of 
fluorine is calcium fluoride, known as fluor spar, CaF 2 . 
This is mixed with sulphuric acid and heated in a plati- 
num retort. A colorless, irritating gas distils over, 
which is caught in water. This solution is the hydro- 
fluoric acid of commerce. It is put on the market usu- 
ally in ceresine or wax bottles. At ordinary tempera- 
tures the gas is believed to have the formula H 2 F 2 . 
Above 30° C. it begins to decompose and at a little be- 



THE HALOGENS 129 

low 90° the density of the vapor indicates a molecular 
weight of 20 which is that for the formula HF. Its 
chief use is for etching glass. The article to be etched 
is covered with paraffin, the design is cut in the wax so 
as to expose the glass, and the hydrofluoric acid is 
dropped on. In a very few minutes the etching is done. 
Graduations upon scientific instruments and apparatus 
such as barometers, burettes, pipettes and the like, are 
thus made. The following equations show the chemical 
reactions in preparing the hydrogen fluoride and the 
glass etching, 

CaF 2 + H 2 S0 4 -» H 2 F 2 + CaS0 4 , 
CaSi0 3 Na 2 Si0 3 + 6H 2 F 2 -» 2NaF + CaF 2 + 2SiF 4 + 6H 2 0. 

The silicon fluoride is a gas and escapes, while the cal- 
cium and sodium fluorides are solids which are washed 
away in cleaning the glass. Porcelain and chinaware, 
in being prepared for hand decoration, are often treated 
with hydrofluoric acid to remove the glazed surface and 
thus cause the gold or other decoration to adhere the 
better. 

Bromine 

14. Where Found. — Bromine in potassium and mag- 
nesium bromide occurs in nature associated with com- 
mon salt. Being more soluble than salt, these com- 
pounds do not crystallize out as readily; hence, they 
are usually found in the upper layers of salt beds. Our 
supply is largely obtained as a by-product of the salt 
works of Ohio, Kentucky and Michigan. 

15. Preparation.— The method is very similar to that 
for the preparation of chlorine. It will be remembered 
that in the laboratory chlorine is made by treating 
manganese dioxide with hydrochloric acid. Hvdrobro- 



130 APPLIED CHEMISTRY 

mic acid is not an article of commerce, because of its 
instability; hence, it must be prepared as needed. If 
magnesium bromide or any other bromide is treated 
with sulphuric acid, hydrogen bromide may be obtained, 
thus, 

MgBr 2 + H 2 S0 4 -> 2HBr + MgS0 4 . 

It has many properties similar to hydrogen chloride in 
that it is a colorless gas, has a very irritating odor, and 
is very soluble in water. For the last reason it con- 
denses moisture in the air or from the breath readily. 
Passed into distilled water, hydrobromic acid is formed, 
but it very soon begins to decompose and in a few days 
no acid at all remains. In preparing bromine, if man- 
ganese dioxide is added to the mixture of magnesium 
bromide and sulphuric acid, we have conditions similar 
to those in the preparation of chlorine. First the hy- 
drogen bromide is formed, then this oxidized by the 
manganese dioxide with the formation of free bromine. 
It is then distilled out and condensed under water. The 
following equation shows the final reaction, 

MgBr 2 + Mn0 2 + 2H 2 S0 4 -* MgS0 4 + MnS0 4 + 2H 2 + Br 2 

16. Physical Characteristics. — Bromine is a dark red- 
dish-brown liquid, the only liquid nonmetallic element. 
It is a little more than three times as heavy as water in 
which it is not greatly soluble — about 3 c.c. in one hun- 
dred. It is a very volatile liquid; hence, if a bottle of 
it is left open it soon passes off into the air. It boils 
at 59° C. and solidifies at - 7.3, in slender, needle-like 
crystals. Its vapors are exceedingly irritating to the 
throat and bronchi, and upon the skin the liquid pro- 
duces serious and painful burns; therefore, the utmost 
care must be exercised in handling it. 

17. Chemical Characteristics. — Many of the character- 
istics of chlorine are observable in bromine, but in a 



THE HALOGENS 131 

less marked degree. A jet of hydrogen burns in a bot- 
tle of bromine vapor producing white fumes due to the 
hydrogen bromide formed. A mixture of the two gases, 
however, is not explosive, but a platinum sponge greatly 
hastens the union as was the case with the chlorine and 
hydrogen mixture. A piece of yellow phosphorus, placed 
in bromine vapor, does not usually ignite, but a slow 
combination takes place, with the formation of phos- 
phorous tribromide. If a small drop of liquid bromine 
be allowed to fall upon a piece of yellow phosphorus, 
the action is immediate. The chemical union is so vi- 
olent that the phosphorus is ignited, bursts into frag- 
ments, and burns vigorously. Small pieces of antimony 
dropped upon bromine in a test tube become red-hot 
almost instantly, float around upon the liquid, and fin- 
ally disappear. The chemical reaction is 

2Sb + 3Br 2 -f 2SbBr 3 . 

With many other metals the action is equally violent. 

18. Uses. — Bromine is used to some extent in the lab- 
oratory in analytical work, but more largely in the 
manufacture of aniline dyes. The compounds, potassium 
and magnesium bromide, are used in medicine, mainly as 
sedatives. 

Iodine 

19. Occurrence. — Like chlorine and bromine, iodine 
in the form of compounds occurs in sea water. From 
this it is separated by certain seaweeds, especially kelp, 
and stored up in the form of rather complicated com- 
pounds. In many places along the Pacific Coast, nota- 
bly, in the neighborhood of San Diego, vast quantities 
of kelp are found, so that ocean vessels are unable to 
make their way through. In the form of compounds, 
sodium iodide and iodate, iodine occurs in the saltpeter 



132 



APPLIED CHEMISTRY 



beds of Chile as bromine does in the salt beds of the 
United States. 

20. Preparation. — Formerly most of the iodine of 
commerce was obtained from seaweeds. They were cau- 
tiously burned so as not to vaporize the iodine present, 
and the ashes were treated as in the preparation of bro- 
mine, that is with manganese dioxide and sulphuric 
acid. The equation is similar: 

2KI + 3H 2 S0 4 + Mn0 2 -> MnS0 4 + 2KHS0 4 + 2H 2 + 1 2 

The iodine distils out and is condensed. It is purified by 
vaporizing again in specially constructed furnaces, shown 




Fig. 30. — Apparatus for purifying iodine by sublimation. 

in Fig. 30. In recent years probably more of the iodine 
supply has come from the deposits in Chile; although 
during the late war in the manufacture of potassium 
and other compounds from kelp much iodine was ob- 
tained as a by-product. 

21. Physical Characteristics. — Iodine is a lustrous, 
nearly black solid. It crystallizes in thin plates, which 
even at room temperature are volatile, as may be seen 
if the crystals are placed in a white dish. Upon warm- 
ing gently it vaporizes without melting. The process is 
called sublimation and is used for purifying iodine and 



THE HALOGENS 133 

other substances which pass directly from the solid to the 
gaseous condition upon heating. It corresponds to the 
distillation of liquids. For medical purposes iodine is 
sublimed more than once as is indicated by the labels 
upon the bottles marked, resublimed. Iodine has an odor 
resembling dilute chlorine. It is very slightly soluble in 
water, barely sufficient to color the solution. However, in 
a solution of potassium iodide in water iodine is very solu- 
ble, giving a dark brown color. The same is true of al- 
cohol and ether solutions, in both of which liquids it is 
very soluble. Carbon disulphide is also an excellent sol- 
vent and gives a beautiful violet solution; starch muci- 
lage is turned deep blue, a reaction which serves as the 
test both for iodine and starch, as may be needed. The 
quantity of iodine should be small, just sufficient to give 
the solution a pale yellow color; otherwise, the starch 
will turn so dark it will appear black. To the eye weak 
solutions of iodine appear not unlike those of bromine. 
They may be distinguished by adding 1 or 2 c.c. of carbon 
disulphide to the solution of iodine or bromine and shak- 
ing well. As the carbon disulphide is a much better sol- 
vent than the water, the bromine or iodine will be col- 
lected in the small quantity of the heavy carbon disulphide 
at the bottom of the test tube. The bromine will give 
a golden brown and the iodine a purple color. 

22. Chemical Characteristics. — These resemble those 
of chlorine, but are much feebler. A crystal of iodine 
laid upon a thin slice of phosphorus reacts vigorously 
so that the phosphorus catches fire and burns, while 
considerable of the iodine is vaporized. Iodine is read- 
ily displaced from soluble compounds by both chlorine 
and bromine, but much more easily by the former. 
Thus, 

2KI + CI. -* 2KC1 + I, 



134: APPLIED CHEMISTRY 

Even a single bubble of chlorine causes a brown dis- 
coloration of the liquid. A very interesting fact about 
iodine is its behavior at high temperatures. In a pre- 
ceding section in this chapter the atomic weight of io- 
dine was mentioned as about 127. Its molecular weight 
is found to be 254, which shows that like chlorine and 
bromine it is diatomic. "When heated above 700° C. the 
vapor becomes lighter and lighter, much more so than 
agrees with Charles' law. until at 1.700 : it is just half 
what it was at 700. This indicates that the molecules 
have been broken into two parts and that the gas is now 
monatomic. The same is true of bromine vapor, but to 
a considerably less extent. It must be noted further 
that as the temperature is lowered the lighter molecules 
recombine to form the diatomic molecules ; at the same 
time a very considerable amount of heat is evolved, just 
as when steam is cooled it gives off the heat previously 
consumed in producing it. The following equation il- 
lustrates what is happening. 

L *± 21. 
The double arrow sign used is read, gives reversibly. 
Such changes are called dissociation, a term which means 
the process of decomposing a substance and reforming 
it under varying conditions. It is probable that at all 
temperatures, between 700 and 1700. the action is pro- 
ceeding in both directions, that is, some of the diatomic 
molecules are being decomposed and others are being re- 
formed by the union of* two monatomics. 

2d. Uses. — Iodine is used mainly in medicinal prepa- 
rations. The tincture, the best known, an alcoholic so- 
lution, is used as a counter-irritant in sprains, bruises 
and swellings ; as a germicide in preventing the spread 
of erysipelas and other similar diseases ; as an antiseptic 
in surgical operations and wounds in place of hydrogen 



THE HALOGENS 135 

peroxide. It is more powerful, more penetrating and 
more lasting, than the peroxide, but at the same time 
much more severe, causes much more irritation, and in 
unskilled hands is much less safe. Iodoform, CHI 3 , is 
a pale-yellow solid; has a peculiar odor, disagreeable to 
most individuals; is strongly germicidal, and often used 
by physicians as an antiseptic in contagious diseases, 
lodothyrin, an extract obtained from the thyroid gland 
of sheep is sometimes used in cases of underdevelop- 
ment of the same gland in the human body. 

Exercises for Review 

1. Name the halogens and state why so called. 

2. Who discovered chlorine? What was the discoverer's idea 
regarding it? What was the old name? Who proved it was an 
element? 

3. Give usual method of preparing and collecting chlorine. 

4. Describe one commercial method of obtaining chlorine. 

5. Give the physical characteristics of chlorine. 

6. Give the chemical characteristics. 

7. Name the important uses of chlorine. 

8. How is hydrogen chloride prepared? Give its character- 
istics. 

9. How is hydrochloric acid prepared? What is muriatic acid? 

10. Give the characteristics of hydrochloric acid. 

11. What can you say of the history of it? Name some uses. 

12. What is aqua regia? Why so called? 

13. Give the uses of hydrofluoric acid. How is it kept for use? 
11. What can you say of the occurrence of bromine? 

15. How is bromine prepared for commerce? Compare method 
with that of chlorine. 

16. Describe bromine. What danger in handling it? 

17. What is the chief use of bromine? 

IS. Where is iodine found? How prepared? 

li). Give the principal characteristics of iodine — physical and 
chemical. 

20. What is sublimation? How is it different from distilla- 
tion? 

21. Give uses of iodine and iodine compounds. 



CHAPTER X 

ACIDS AND BASES 
Outline — 

Oxides, Basic and Acidic 

Acids 

Bases 

.Nomenclature of Compounds 

(a) Acids 

(6) Bases 
Neutralization 
Salts 

(a) Normal or Neutral 

(b) Acid 

(c) Basic 

(d) Nomenclature 

(e) Binary 

1. Oxides. — An oxide is a compound consisting of only 
two elements one of which is oxygen. Since oxygen 
combines with all the elements except fluorine and the 
argon group, we should expect there would be a very 
large number. Already we have met with several. Mer- 
curic oxide has been used in preparing oxygen; man- 
ganese dioxide as a catalyst in making oxygen and in 
the preparation of chlorine, bromine and iodine. When- 
ever we have burned a metal in oxygen or the air, as 
for example iron or magnesium, we obtained an oxide. 
Likewise, when phosphorus and sulphur were burned in 
oxygen or in the air their oxides were produced. 

2. Two Classes of Oxides. — If oxides, such as will re- 
act with water, are put with water, some will be found 
to give a sour taste, and will turn litmus paper red, 
while others thus treated, have a soapy taste and turn 
reddened litmus paper blue. When Lavoisier gave the 

136 



ACIDS AND BASES 137 

name, oxygen, meaning acid former to the gas, he did not 
recognize the fact that a chemical change takes place be- 
tween certain oxides and water, but considered the oxides 
themselves as acids. Such oxides as react with water to 
form acids are called acidic oxides, or anhydrides, and 
those that form hydroxides with the water are called basic 
oxides. Typical of the former class are those obtained 
when sulphur and phosphorus were burned in oxygen. 
With water they react thus, 

S0 2 + H 2 ->H 2 S0 3 , 
P 2 5 + H 2 ^2HP0 3 . 

The most familiar basic oxide is lime. When treated with 
water vigorous chemical action results accompanied by 
great heat. The equation is 

CaO + H 2 -» Ca(HO) 2 

Similar reactions are those of sodium and potassium ox- 
ides with water, 

Na 2 + H 2 -> 2NaHO, 
K 2 + H 2 -» 2KHO. 

A careful study of the various oxides shows that, gener- 
ally speaking, those of the metals react with water more 
or less rapidly to produce oases, while those of the non- 
metalic elements are anhydrides, or acid-forming oxides. 
3. Acids. — It has been said elsewhere that all acids 
contain hydrogen. Most of them also contain oxygen. 
If all were formed by the union of an oxide with water, 
all would necessarily contain oxygen. A few, such as 
the acids of the halogens, hydrofluoric and others, are 
solutions of certain compounds and are not formed by 
the interaction of some oxide with water. In all of 
them, however, the hydrogen forms the positive part of 
the compound, while the other element together with 



138 APPLIED CHEMISTRY 

the oxygen when present, constitutes the negative part. 
It is the hydrogen in a peculiar condition which will 
be discussed later that causes all acids to turn litmus 
red. 

4. Bases. — Theoretically, at least, all bases may be 
formed by the interaction of a metallic oxide and water ; 
naturally therefore, all must contain a metal, hydro- 
gen and oxygen, since the action is an additive one. 
They are all called hydroxides, a term which indicates 
that they contain hydrogen and oxygen. There is no ex- 
ception to this. One base is known, however, which con- 
tains no metal, ammonium hydroxide, XH 4 H0, but the 
chemical group, XH 4 — shows many of the characteristics 
of a metal. The soluble bases are called alkalies; they 
are potassium hydroxide, sodium hydroxide, ammonium 
hydroxide, and those of barium, strontium and calcium. 
The blue litmus test which they give is due to the hydroxyl 
group. HO, which they all contain, and which is the only 
thing common to all. 

5. Nomenclature. — Little need be said about how bases 
are named. They are all called hydroxides with the 
name of the metal prefixed, thus: Cu(HO) 2 is called cop- 
per hydroxide and Al(HO) 3 is aluminum hydroxide. In 
a preceding chapter the gas, HC1, has been spoken of as 
hydrogen chloride. This is for the reason that when per- 
fectly free from water it shows no acid properties. Like- 
wise, we should expect a compound with the formula 
H 2 S0 4 to be called hydrogen sulphate; H 2 C0 3 , hydrogen 
carbonate ; HXO,,, hydrogen nitrate. They are all acids 
as the formulas indicate and this plan would be in accord- 
ance with what has been said in Chapter I. Attempts 
have been made to adopt such a nomenclature, but as sev- 
eral of the familiar acids were discovered and in common 
use before there was anv svstem in the naming of com- 



ACIDS AND BASES 139 

pounds, such efforts have met with failure. Accordingly, 
in the oxygen acids the electronegative element suggests 
the name. Thus, in the three given above, sulphur, car- 
bon and nitrogen have given the respective names. This 
is true, generally. However, there are many cases in 
which there are two or more acids formed from the same 
three elements. Thus sulphur has 

H 2 S0 4 Sulphuric, 

H 2 S0 3 Sulphurous, 

H 2 S0 2 Hyposulphurous, 
and chlorine forms 

HC10 4 Perchloric, 

HCIO3 Chloric, 

HC10 2 Chlorous, 

HCIO Hypochlorous. 

In such case the quantity of the oxygen determines the 
ending of the name. It is usually true that the most com- 
mon acid in any group has a name ending in it; then, 
the one with a smaller amount of oxygen next to this is 
given the same name with the ending changed to ous. If 
there be others, the prefixes hypo, meaning under, and 
per, meaning beyond or above, are used. This is seen in 
the four chlorine acids given above. In the case of the 
acids containing no oxygen the prefix hydro is used in 
all cases, thus, 

H 2 F 2 Hydrofluoric, 

HC1 Hydrochloric, 

HBr Hydrobromic, 

HI Hydriodic 

H 2 S Hydrosulphuric. 

6. Neutralization. — If a base and an acid are 
brought together in suitable proportions, chemical ac- 
tion takes place, in which both are destroyed and new 



140 APPLIED CHEMISTRY 

compounds are formed. The process is called neutraliza- 
tion, for the reason that when the two are exactly propor- 
tioned the compound resulting affects neither red nor 
blue litmus paper. The following equations illustrate 
a few cases, 

Ca(HO) 2 + H 2 S0 4 -* CaS0 4 + 2H 2 0, 

KHO + HC1 -^KC1 + H 2 0, 
Ba(HO) 2 + 2HCl -> BaCl 2 + 2H 2 0, 

NaHO + HN0 3 -> NaN0 3 + H 2 0, 
2NaHO + H 2 C0 3 -^ Na 2 CO s + 2H 2 0. 

It will be noticed in all these cases that one of the pro- 
ducts is water. The other is a compound which is not a 
base since it does not contain hydroxyl; it is not an acid 
since it has no positive hydrogen. It is a new compound. 
All such, produced by the union of a base and an acid, or 
by a similar process, are called salts. This name was 
given for the reason that a very large number of them 
resemble common salt and may be formed the same way. 
7. Classes of Salts. — All those shown in the equations 
just above are called neutral or normal salts, because 
the hydrogen has all been removed from the acid and the 
hydroxyl from the base, so that generally speaking they 
should affect neither red nor blue litmus. However, such 
proportions of the acid or base might be used as to leave 
some hydrogen from the acid or some hydroxyl from the 
base not thus neutralized. For example, 

H 2 S0 4 + NaHO -> NaHS0 4 + H 2 0, 

H 3 P0 4 + NaHO -> NaH 2 P0 4 + H 2 0, 

H 3 P0 4 + 2NaHO -» Na 2 HP0 4 + 2H 2 0, 

H 3 P0 4 + 3NaHO -> Na 3 P0 4 + 3H 2 6. 

In three of the above equations some of the hydrogen re- 
mains in the salt obtained and should give the test. In 
fact, frequently in such salts the sour taste of the acid is 



ACIDS AND BASES 141 

still very noticeable and blue litmus is quickly reddened. 
All such are called acid salts: they are very common. 
Obviously such an acid as hydrochloric could not form 
an acid salt. It must be observed further, that not all 
salts containing hydrogen are acid salts. Thus, 

NH 4 H0 + HNO s -> NH 4 N0 3 + H 2 0, 
NaHO + HC 2 H 3 2 -> NaC 2 H 3 2 + H 2 0. 

Both the salts formed in these equations contain hydro- 
gen, yet both are neutral salts. In both cases all the 
positive hydrogen has been removed from the acid. In 
the first one, the hydrogen remaining in the salt was ob- 
tained from the base, and belongs to the group, NH 4 . In 
the second, only the hydrogen atom written by itself is 
positive: the other three are combined in the group 
C 2 H 3 2 which is a radical and the hydrogen is not free 
to act alone. On the other hand, there might be more 
hydroxyl groups present in the base used than the hydro- 
gen in the acid could remove in the formation of water. 
Thus, 

2Cu(HO) 2 + H 2 C0 3 -> 2H 2 + Cu 2 (HO) 2 C0 3 . 

Usually this is written CuC0 3 .Cu(HO) 2 . Such salts 
are not as common as the acid salts, but they do appear 
and are formed in various ways. They are called oasic 
salts. The above is called basic copper carbonate. 

8. Nomenclature of Salts. — The common salts offer no 
difficulties to the student in their nomenclature. Thus, 

KBr Potassium bromide 

ZnCl 2 Zinc chloride 

K 2 S Potassium sulphide 

CuS0 4 Copper sulphate 

NaNOjj Sodium nitrate 

CaCO, Calcium carbonate, 



142 APPLIED CHEMISTRY 

KCIO3 Potassium chlorate, 

Na 3 P0 4 Sodium phosphate, 

KIO3 Potassium iodate, 

KBr0 3 Potassium bromate. 

Compounds with two elements have names ending in 
ide; while the others end in ate unless formed from an 
acid whose ending is ous when the salt has a name end- 
ing in He. The difficulty is with the compounds formed 
from the same three elements used in different propor- 
tions. Thus, 
Na 2 S0 4 Sodium sulphate, formed from H 2 S0 4 sulphuric 

acid, 
Na 2 S0 3 Scdium sulphite, formed from H 2 S0 3 sulphur- 
ous acid, 
Na 2 S0 2 Sodium hyposulphite, formed from H 2 S0 2 , hy- 

posulphurous acid, 
and 

KC10 4 Potassium perchlorate from HC1 4 perchloric acid, 
KClOg Potassium chlorate from HC10 3 chloric acid, 
KC10 2 Potassium chlorite, from HC10 2 chlorous acid, 
KCIO Potassium hypochlorite, from HCIO hypochlo- 

rous acid. 
Only memorizing the formulas of the acids in the series, 
and the fact that oxygen acids ending in ic give salts end- 
ing in ate; and ending in ous, salts ending in ite can suf- 
fice. However, most of these are not of sufficient import- 
ance in warranting the beginner in making the attempt. 
Again, the acid salts offer some trouble, thus, 

K 2 S0 4 is potassium sulphate, 

KHS0 4 is acid potassium sulphate or potassium hydro- 
gen sulphate. As there can be only one acid potassium 
sulphate no confusion results from the use of either term. 



ACIDS AND BASES 



143 



But tribasic acids, like phosphoric, H 3 P0 4 , yield two acid 
salts, thus, 

K 3 P0 4 Potassium phosphate, 
K 2 HP0 4 Dipotassium phosphate, 
KH 2 P0 4 Monopotassium phosphate. 

As the last two are both acid salts they could not be 
read acid potassium phosphate, for either might be meant. 
It is customary, therefore, to follow the plan suggested, 
in which the amount of the base used is indicated by the 
prefix di or mono. The fact that one hydrogen remains 
from the acid in the salt is implied by the prefix di, for 
the reason that the acid originally contained three hydro- 
gen atoms and only two have been replaced. Likewise, 
mono implies that two atoms of hydrogen remain in the 
salt. 

9. Binary Salts. — Compounds of two elements are 
called binaries. Such are all salts made from the binary 
or no-oxygen acids. Their nomenclature offers no diffi- 
culty except in cases of two or more formed from the 
same two elements. When such is the case, the endings, 
ous and ic are used just as has been said in the acid end- 
ings. The one ending in ous always indicates the one 
full of or having the greater relative amount of the posi- 
tive part of the compound. Thus, 

Hg 2 Mercurous oxide, 

HgO Mercuric oxide, 

FeCl 2 Ferrous chloride, 

FeCl 3 Ferric Chloride, 

HgCl 2 Mercuric chloride, 

Hg 2 Cl 2 Mercurous chloride, 

Sn0 2 Stannic oxide, 

SnO Stannous oxide. 

Oftentimes prefixes are used which may lessen the dif- 



144 APPLIED CHEMISTRY 

ficulty. Thus, manganese dioxide indicates the amount 
of the oxygen; again old forms, now obsolete, are some- 
times used which are often obscure. Thus, Fe 2 3 is 
sometimes called iron sesquioxide, instead of ferric oxide. 
The prefix means a ratio of two to three and was applied 
to such compounds as the one just given. Proto and sub, 
meaning the first and under are also used applied to the 
lowest of the compounds in a series. 

Exercises for Review 

1. What is an oxide? Name two classes, define each and give 
examples. 

2. What can you give for the composition of acids? What 
two tests do they give? 

3. Give the composition of bases? What tests do they give? 

4. What is an alkali? Name five. 

5. How are bases named? Acids? 

6. Give names of HC10 3 , HI0 3 , HBr, HBr0 3 , H 2 S0 4 , H 3 P0 4 , 
Ba(HO) 2 , Ca(HO) 2 NaHO. 

7. What is meant by neutralization? Write an equation illus- 
trating. 

8. Complete the following equations: 

H 2 S0 4 -i-Cu(HO) 2 ->, 
HCl + Ba(HO) 2 -», 
CaO + H 2 S0 4 -», 
Zn(HO) 2 + H 2 S0 4 -*, 
ZnO + H 2 S0 4 -> , 
Zn + H 2 S0 4 -> . 

9. How many salts were obtained in the above equations? 
Were any formed without the use of a base? Why was this? 

10. What is a salt? Name three kinds. Define each and give 
examples. 

11. Which of the following are acid salts: KN0 3 , KHS0 4 , 
CuS0 4 , AgNO s , K 2 HP0 4 , KH 2 P0 4 , K,P0 4 , CaH 2 (C0 3 ) 2 ? 

12. Give names of all formulas in question 11. 

13. What is a binary compound? Illustrate. 

14. Give names of FeO, Fe 2 3 , FeCl 3 , FeCl 2 , CuS, Cu 2 S, H 2 0, 
H 2 2 , Hg 2 0, HgO. 



CHAPTER XI 
NITROGEN AND COMPOUNDS 



ine — 

Nitrogen 




(a) 


Occurrence 


m 


Preparation from the Air 


(<0 


Preparation from Chemicals 


(<?) 


Characteristics 


Ammonia 




(a) 


Occurrence 


(&) 


Commercial Supply 


(<0 


Uses 


Oxides of 


Nitrogen 


Nitric Acid 


(a) 


Preparation 


m 


Characteristics 


(o) 


Uses 


Explosives 




(a) 


Gunpowder 


m 


Nitroglycerine 


(<0 


Dynamite 


(d) 


Nitrocellulose 


(e) 


Smokeless Powders 


(/) 


Picrates 


(g) 


T.N.T. 


Other Products 


(a) 


Collodion 


(&) 


Celluloid 


(<0 


Fiber Silk 



1. Occurrence of Nitrogen. — In another chapter it has 
been seen that nitrogen constitutes about four-fifths of 
the air. It is found in many compounds in nature, es- 
pecially the nitrates of sodium and potassium. The 
former occurs in large quantities in Chile, whence it is 

145 



146 



APPLIED CHEMISTRY 



exported to all parts of the world. Nitrogen is an im- 
portant constituent of such food products as lean meat, 
eggs, beans and peas, and is found to some extent in 
grains, wood, coals and like substances. Some varieties 
of coal contain in the neighborhood of 2 per cent. 

2. Preparation. — By removing the other constituents 
of the air, nitrogen may be obtained comparatively pure 
except for the admixture of the argon. This is generally 
done by the use of phosphorus or by passing a stream 
of air over heated copper turnings. The proportion of 
nitrogen in the air may be shown somewhat approxi- 




Fig. 31. — Method of determining approximately the proportion of nitrogen 

in the air. 



mately by apparatus shown in Fig. 31. A graduated 
cylinder is inverted over a deflagrating spoon with 
handle bent as shown. Into the spoon is put a piece of 
yellow phosphorus the size of a small bean; then the 
whole is placed over a trough of water and the cylinder 
clamped so that the water level inside and out is at the 
zero mark. The phosphorus will slowly combine with 
the oxygen and at the end of two or three days the 
water level will have become stationary except for at- 
mospheric changes of pressure and temperature. The 



NITROGEN AND COMPOUNDS 147 

volume of the residual nitrogen and argon may then 
be read off. From compounds nitrogen is generally pre- 
pared by gently heating a solution of ammonium chlo- 
ride and sodium nitrite. The following equations illus- 
trate the changes taking place, 

NH 4 Cl + NaN0 2 -» NaCl + NH 4 N0 2 , 

NH 4 N0 2 -> N 2 + 2H 2 0. 

3. Characteristics of Nitrogen. — Nitrogen is a color- 
less gas, slightly lighter than air, may be liquefied at 
-194° C. and solidified at -214° C. It is much less solu- 
ble in water than oxygen. Chemically, it is a very in- 
active element; it will not burn or combine with many 
of the elements directly. Passed over strongly heated 
magnesium or calcium it will form a nitride with them. 
It was by passing nitrogen over heated magnesium that 
argon was discovered, since it will not combine with 
magnesium. By means of a powerful electric dis- 
charge through a mixture of oxygen and nitrogen, chem- 
ical union takes place between these two elements with 
the formation of one or more oxides of nitrogen. Like- 
wise a mixture of hydrogen and nitrogen, three parts 
to one, by means of the electric spark is slowly changed 
into ammonia. The uses of nitrogen have been dis- 
cussed in the chapter on the atmosphere. 

4. Occurrence of Ammonia. — Because of the fact that 
certain waste products of the animal economy, as well 
as other nitrogenous bodies in their decomposition, pro- 
duce ammonia in appreciable quantities, it has long been 
familiar to scientists. For many years it was sold in 
solution under the name " spirits of hartshorn" be- 
cause of the fact that it was formerly obtained by the 
distillation of the horns of deer and cattle. 

5. Commercial Supply.— Some varieties of ordinary 
soft coal contain nitrogen in appreciable quantities, in 



148 APPLIED CHEMISTRY 

the form of compounds. When such coals are heated 
the nitrogenous bodies are decomposed and the nitrogen 
comes off as ammonia, NH 3 , mixed with a great variety 
of other gases. On account of its high solubility it may 
be largely separated from the others by passing through 
towers or cylinders containing coke or something simi- 
lar, kept moist by dripping water. This very impure 
solution, called gas liquor is drawn off, lime is added and 
the mixture is boiled. The ammonia distils out and is 
passed into either hydrochloric or sulphuric acid, when 
the chloride or sulphate of ammonia is formed, 

NH 3 - HC1 -* NH 4 C1, 
2NH 3 + H 2 S0 4 -> (NHJ 2 S0 4 . 

By treating a solution of either of these salts with lime 
and passing the gas into distilled water, pure ammonium 
hydroxide or aqua ammonia is obtained, 

(NHJ 2 S0 4 + CaO -> CaS0 4 -2XH 3 -H 2 0, 
NH 3 + H 2 -> NH 4 HO. 

6. Characteristics of Ammonia. — Ammonia is a color- 
less gas, with very pungent odor. It is exceedingly sol- 
uble in water so that about 1,200 liters will dissolve in 
1 liter of water at 0° C. Putting it into other words, one 
quart of ice water will absorb nearly six barrels of am- 
monia gas. It may be liquefied at -38.5 C. and solidified 
at -77° C. The strong ammonia water of commerce con- 
tains about 35 per cent of the gas with a specific gravity 
of 0.88. At ordinary temperatures, except under pres- 
sure, water will hold only about 28 per cent of ammonia, 
and at 100° the ammonia is entirely expelled. 

7. Uses of Ammonia. — Its principal use is in the liquid 
form for refrigeration purposes. From a container the 
liquid is allowed to pass through a needle valve into 
pipes surrounded by a solution of salt, of such strength 



NITROGEN AND COMPOUNDS 



149 



that its freezing point is much lower than that of pure 
water. A pump is constantly withdrawing the gasified 
ammonia, thus maintaining a partial vacuum, so that 
a rapid evaporation of the ammonia is secured. The 
rapidity of the evaporation causes a lowering of the 
temperature of the pipes and the surrounding brine, 
which is kept circulating by a special brine pump. For 
cold storage purposes this brine is forced through pipes 
to any place desired: in this way meats, fruits, but- 



WATER TANK 
\ZZZZZZZZZZZ 1 V ^Ld^Z^LL 



\Kl\\\ll 



mm 



m 



1 ;pB 



CONDENSER 
PIPES 



LIQUID NH, 



t/EEDLE VALVE 




BRINE TANK 










Fig. 32. — Manufacture of ice. 



ter, eggs, and all other perishable food products may be 
kept near the freezing point for long periods. For pro- 
tection against moths, furs and woolen clothing are often 
stored thus in the summer. Temperatures low enough 
to freeze meats may easily be secured; fishing vessels, 
gone on long trips, often return after months with their 
cargo of fish frozen solid. Markets, floral shops, and 
various other places employ these methods of preserving 



150 APPLIED CHEMISTRY 

their goods; everyone has seen the brine pipes, heavily 
coated with frost, which furnish the cold for such pur- 
poses. For the manufacture of ice, galvanized iron 
boxes filled with pure water are lowered into the brine 
tank. In from sixty to seventy-two hours the water has 
become solid, whereupon the container with the ice is 
lifted from the brine ; a stream of warm water is run 
over it for a moment to loosen the ice, when it slips out 
and slides down into the storage room. Fig. 32 shows 
the main steps in the process. When the ammonia is 
withdrawn from the pipes it is again compressed and 
in summer time is cooled by streams of running water, 
whereby it again becomes a liquid. It is said that to 
make 3 pounds of ice requires about 1 pound of ammo- 
nia, but as the liquid is used over and over again the 
process is very cheap. In the household, ammonia is of- 
ten used in a dilute solution for softening water and for 
similar purposes. In commerce it finds extensive use in the 
manufacture of cooking soda and of sodium carbonate. 
The process will be described elsewhere in the text. 

8. The Oxides. — There are five oxides of nitrogen 
known. They are: 

Nitrous oxide, Nitrogen monoxide, N 2 0, 

Nitric oxide, Nitrogen dioxide, NO, sometimes written 
N 2 2 , 

Nitrous anhydride, Nitrogen trioxide, N 2 3 , 

Nitrogen peroxide, Nitrogen tetroxide, N0 2 , also writ- 
ten, N 2 4 , 

Nitric anhydride, Nitrogen pentoxide, N 2 5 . 

About the only facts of interest regarding the third and 
fifth in the series are that they are the anhydrides of 
acids, thus, 

N 2 3 + H 2 -> 2HN0 2 , Nitrous acid, 
N 2 5 + H 2 -^ 2HN0 3 , Nitric acid. 



NITROGEN AND COMPOUNDS 151 

Nitric oxide is mentioned for the reason that almost in- 
variably when nitric acid is added to a metal, it is pro- 
duced. However, it is never seen unless precautions are 
taken to collect it over water, because of the fact that 
as soon as exposed to the air it combines spontaneously 
with oxygen and forms the tetroxide. Thus, 

3Cu + 8HN0 3 -* 2NO + 4H 2 + 3Cu(N0 3 ) 2 ; 
2NO + 2 -> 2N0 2 . 
The peroxide is a heavy, reddish-brown gas resembling 
bromine vapor, with very irritating odor. It is very sol- 
uble in water with which it reacts, thus, 
2N0 2 + H 2 -* HN0 3 + HN0 2 . 

9. Nitrous Oxide. — Nitrous oxide may be prepared by 
cautiously heating ammonium nitrate, thus, 

NH 4 N0 3 -> N 2 + 2H 2 0. 
As it is somewhat soluble in cold water it must be col- 
lected over warm water. It is a colorless gas, with a very 
faint pleasant odor. In it various substances will burn 
when ignited almost as well as in oxygen and a spark 
on a pine splinter will burst into flame. It becomes 
a liquid at about -90° C. and a solid at -102° C. If in- 
haled it produces insensibility and mixed with oxygen it 
is frequently used as an anesthetic for minor surgical 
operations such as the extraction of teeth. It is some- 
times called laughing gas, because of its intoxicating ef- 
fects upon some individuals. 

10. Nitric Acid. — It is said that occasionally, after un- 
usually violent electrical storms accompanied by little 
rain, traces of nitric acid have been found in the water 
which has fallen. As nitric acid is an oxyacid it should 
be able to be formed in this manner. 

11. Commercial Preparation. — In the laboratory and 
commercially up to very recent times nitric acid lias 



152 



APPLIED CHEMISTRY 



always been prepared by treating sodium nitrate with 
sulphuric acid, thus, 

NaN0 3 + H 2 S0 4 -» NaHS0 4 + HN0 3 . 
The laboratory form of apparatus is shown in the illus- 
tration. No corks, either rubber or otherwise, may be 
used as they are rapidly attacked by the fumes. From 
the fact that during the war, trade with Chile was 
largely interrupted so that adequate supplies of sodium 
nitrate could not be obtained, other methods had to be 
adopted. Consequently, preparation from the air dur- 
ing the last years of the war was carried on extensively. 
At points where electricity of high voltage could be ob- 




Fig. 33. — Preparation of nitric acid. 



tained cheaply from water power, by electric discharge 
through a slowly moving current of air, certain oxides 
of nitrogen are obtained. These are passed into water 
with the formation of nitrous and nitric acid, 



H 2 + N 2 3 

2N0 2 + H 2 -> 

N 2 5 + H 2 



-^ 2HN0 2 , 
HN0 2 + HN0 3 , 
■4 2HNO,. 



As nitrous acid readily takes up more oxygen and be- 
comes nitric, the ultimate product ig nitric. It is prob- 



NITROGEN AND COMPOUNDS 153 

able that this method in some form will eventually dis- 
place the older one of obtaining nitric acid from salt- 
peter. 

12. Characteristics of Nitric Acid. — When pure, ni- 
tric acid is a colorless liquid, but exposed to bright sun- 
light, or heated, decomposition takes place with the 
formation of sufficient peroxide to color the liquid more 
or less brown. It boils at 86° C. and solidifies at -47° C. 
The concentrated acid of commerce contains 68 per cent 
nitric acid, with a specific gravity of 1.42. Upon the 
hands or clothing it produces a yellowish-brown stain, 
which cannot be removed by ammonia as can those of 
hydrochloric acid. It is a strong oxidizing agent, for 
reasons shown by the equation, 

2HN0 3 -> H 2 + 2N0 2 + 0. 
From the fact that it thus readily yields free oxygen 
it reacts differently with metals from that of other acids 
thus far mentioned. Instead of giving up hydrogen as 
do hydrochloric and sulphuric, when put with a metal, 
as iron or zinc, it converts the metal into an oxide. 
Then, this oxide often dissolves in other portions of the 
acid present and forms a nitrate. For example, copper 
reacts with nitric acid forming copper nitrate, Cu(N0 3 ) 2 
and nitric oxide and water but no hydrogen. The 
changes which may be presumed to take place may be 
represented thus, 

3Cu + 2HN0 3 -* 3CuO + H 2 + 2N0, 
3CuO + 6HN0 3 -> 3Cu(N0 3 ) 2 + 3H 2 0. 
Adding the two equations together we have the result 
as obtained by the actual experiment, 

3Cu + 8HN0 3 -^ 3Cu(N0 3 ) 2 + 4H 2 + 2N0. 
13'. Uses. — One of the most important uses of nitric 
acid is in the manufacture of explosives, Gunpowder, 



154 APPLIED CHEMISTRY 

while not made from nitric acid, contains potassium or 
sodium nitrate, both of which are salts of nitric acid. 
The other constituents are sulphur and charcoal, but the 
nitrate forms 75 per cent of the whole. Being a mix- 
ture, an appreciable length of time is required for the 
combustion to proceed throughout the entire mass; 
hence, gunpowder is a low power explosive. Among 
those of high power, glyceryl nitrate, commonly called 
nitroglycerine, is one of the longest known. It is pre- 
pared by treating glycerine with fuming nitric acid. 
The reaction, 

C 3 H 5 (HO) 3 + 3HN0, -> C 3 H 5 (N0 3 ) 3 + 3H 2 0, 

shows that for every molecular weight of nitroglycerine 
produced there are three of water formed. In a short 
time this would so dilute the nitric acid that chemical 
action would cease, or become exceedingly slow. It be- 
comes necessary, therefore, to remove it. This is clone 
by introducing continuously with the nitric acid fuming 
sulphuric, which as we have seen is a great absorbent of 
water. In this way the process becomes continuous. Ni- 
troglycerine is a heavy, oily liquid, and for this reason 
not convenient to handle or transport. Much of it is 
therefore made into dynamite or giant powder and other 
explosives. By mixing with it sawdust or kieselguhr, 
a silicious earth of tubular structure, both of which have 
high absorbtive powers for nitroglycerine, dynamite is 
prepared. It is commonly sold under the name of giant 
powder with percentages of nitroglycerine ranging from 
25 to 75. It is used in the form of sticks or in coarse 
granules. Such explosives as these are fired by a detona- 
tor, such as mercuric fulminate, Hg(CNO) 2 , commonly 
called fulminating mercury. This compound is decom- 
posed by a sharp blow, giving a spark and heat sufficient 



NITROGEN AND COMPOUNDS 155 

to begin the decomposition of the main explosive. All 
explosives contain combustible material and within them- 
selves oxygen sufficient or nearly so to burn completely. 
In two nitroglycerine molecules, 2C 3 H 5 (N0 3 ) 3 , there are 
6 atoms of carbon and 10 of hydrogen. The hydrogen 
requires 5 atomic weights of oxygen for its combustion 
and the carbon 12. By looking at the formula it will 
be seen that the oxygen is a little more than sufficient, as 
the nitrogen is set free and passes off in this condition. 
It is apparent, therefore, that the liquid or solid, except- 
ing the inert material used, is entirely converted into 
gases of very great volume, which through the heat gen- 
erated are enormously expanded ; coming almost instan- 
taneously the pressures are tremendous and the results 
terrific. 

14. Nitrocellulose. — This is commonly called guncot- 
ton. Cellulose, of which filter paper or cotton is largely 
composed, has the formula, (C 6 H 10 O 5 ) n . Into this mole- 
cule we may introduce nitrate groups as in the case of 
the glycerine and by the same method. Water is a by- 
product and must be removed as before. In this case 
any number of nitrate groups may be substituted, from 
three to six, the hexanitrate being much more explosive 
than the compounds with fewer nitrate groups. The 
following equation shows the reaction, 

2C 6 H 10 O 5 + 6HN0 3 -> C 12 H 14 4 (N0 3 ) 6 + 6H 2 0. 

The products of the explosion are the same as before. 
Guncotton is safe to handle if kept damp and in this 
condition it is uniformly transported on shipboard or 
elsewhere. Even when damp it may be exploded by the 
use of a detonator or electric spark with a small amount 
of dry to start the process. It is used in mining harbors 
or other places against attack as well as for other simi- 



156 



APPLIED CHEMISTRY 



lar purposes. The ternitrate, being much less explo- 
sive, when dissolved in a mixture of alcohol and ether, 
is sold under the name collodion. It is a viscous, quick- 
drying liquid, used in photography, and as new skin, so- 
called, in medicine. For the latter purpose a small per 
cent of Venice turpentine and castor oil is added to ren- 
der it more flexible and less liable to crack when dried 
upon the skin. If a solution of camphor in alcohol is 
used as a solvent for the guncotton, celluloid is obtained, 
the uses of which are familiar. Fiber silk is another 
product closely related. The guncotton, by one method, 
is dissolved as in making collodion: when it has reached 




Fig. 34. — Some forms of smokeless powder. 



a thick, viscous stage it is forced through tiny openings 
like those in the spinneret of the spider or silk worm. 
These threads dry instantly upon coming into the air, 
are wound on bobbins and made into cloth as if real silk. 
The explosive nitrate groups must be removed and this is 
done by treatment with an alkali or with calcium sul- 
phide. The luster is not greatly different from that of 
real silk, but the fibers are more brittle and the wearing 
qualities as a result inferior. 

15. Smokeless Powders. — Two varieties are sold under 
the names, cordite and oallistite. The former is a mixture 



NITROGEN AND COMPOUNDS 157 

of nitroglycerine and guncotton with a little vaseline 
added. Ballistite is a mixture of the same two ex- 
plosives to which is added a small amount of diphen- 
ylamine, which reduces the explosive character. Other 
varieties are simply the hexanitrate cellulose dissolved 
and molded into various shapes, some of which are 
shown in Fig. 34. 

16. Picric Acid and T. N. T. — Picric acid with the' 
formula, C 6 H 2 (N0 2 ) 3 OH, is obtained from phenol, com- 
monly known as carbolic acid, C 6 H 5 OH, in which have 
been substituted three nitro groups for three of the hy- 
drogen atoms. This will be seen by examining the two 
formulas. It is a very explosive substance and from it a 
very considerable number of high explosives have been 
prepared. An intimate mixture of red lead, Pb 3 4 , with 
about an equal volume of picric acid makes a powerful 
explosive which may be fired by heat alone. During the 
war a great deal was heard about the explosive, T.N.T. 
and its terrific power. Toluol is a compound closely re- 
lated to phenol, with the formula, C 6 H 5 CH 3 . The group, 
CH 3 , has taken the place of hydroxyl, HO, in the phenol. 
T.N.T. is trinitrotoluol, with the formula, C G H 2 (N0 2 ) 3 - 
CH 3 , which will be observed is toluol with three hydrogen 
atoms replaced by nitro groups. When exploded the pro- 
ducts are not essentially different from those already de- 
scribed elsewhere. 

Exercises for Review 

1. State where nitrogen occurs in nature. What food products 
contain it? 

2. How is nitrogen obtained from the air? How from chemicals? 

3. Describe nitrogen. How was argon discovered? 

4. How do you account for the presence of ammonia in the air? 

5. What is spirits of hartshorn? 

6. State how ammonia is prepared for commerce. Write the 
equations. 



158 APPLIED CHEMISTRY 

7. Describe ammonia. 

8. Give important uses of ammonia. 

9. Name the oxides of nitrogen and give formulas. 

10. How is nitrous oxide prepared? Chief use? 

11. How is nitric acid prepared? Equation. 

12. Explain how nitric acid is made synthetically. What led to 
this? 

13. Give chief properties of nitric acid. Why is it an oxidizing 
agent? 

14. Give important uses of nitric acid. 

15. How is nitroglycerine made? Dynamite? When exploded, 
what forms? 

16. What is nitrocellulose? Collodion? Celluloid? Fiber silk? 

17. Name two smokeless powders. State how made. 

18. What is T.N.T.? 



CHAPTER XII 

CARBON 

Outline — 

Occurrence in Nature 
Allotropic Forms of Carbon 
Characteristics of Carbon 
Diamonds 

(a) Origin 

(6) Uses 
Graphite, Compared with the Diamond 

Uses 
Coals, How Produced in Nature 

Varieties 
Petroleum 

(a) Origin 

(&) Kinds 

(c) Products obtaiiied by Distillation 
Natural Gas 
Charcoal 

(a) Kinds 

(b) Uses 
Lampblack 
Coke 

Gas Carbon 
Carbon Monoxide 

(a) Formation 

(&) Characteristics 
Carbon Dioxide 

(a) Preparation 

( b ) Characteristics 

(c) Uses 

Other Carbon Compounds 

1. Occurrence of Carbon. — The relative amount of 
carbon in nature is not large. It will be remembered 
that it is not among the eight most abundant elements 

159 



160 APPLIED CHEMISTRY 

which constitute almost the entire amount of the matter 
composing the earth. However, in the form of com- 
pounds it is familiar in a very great variety. In fact, 
so numerous are they that they constitute an entirely 
separate branch of chemistry, called organic, for the 
reason that years ago they were supposed to be produced 
by organized or life forces alone. The muscles of the 
body consist largely of proteins, composed mainly of car- 
bon, hydrogen, oxygen and nitrogen. The stems of plants 
and trunks of trees are largely cellulose, containing car- 
bon, hydrogen and oxygen. The mineral world furnishes 
the corals, limestone, marble, calcite, dog tooth spar, and 
many other carbon compounds. It is some form of car- 
bon that constitutes the fuel of the world ; carbon com- 
pounds in the form of starches, sugars and fats furnish 
heat and energy for the human body, while protein foods, 
similar compounds of carbon containing nitrogen, are nec- 
essary to rebuild the wasted muscles. Carbon thus be- 
comes a very interesting and a very important element. 

2. Forms of Carbon. — The only pure form of carbon 
is the diamond. Graphite, however, although in appear- 
ance it is entirely different, is nearly pure ; closely re- 
lated are anthracite coal and the artificial forms, coke, 
charcoal, gas carbon and lampblack. Other varieties 
of coal contain less free carbon and more bituminous 
compounds of carbon, hydrogen and nitrogen. Graphite 
may be considered a crystallized, allotropic form of the 
diamond, and lampblack an amorphous or uncrystallized 
allotrope. 

3. Some General Characteristics. — The physical prop- 
erties of carbon are so entirely different in the three 
allotropic forms that they must be considered sepa- 
rately. The crystallized varieties will burn only at very 
high temperatures and in an atmosphere of oxj^gen; the 



CARBON 161 

amorphous forms, especially the more impure, burn 
readily in the air without the addition of great heat. 
At high temperatures carbon combines Avith various 
elements to form carbides. It is a strong reducing agent 
also at red heat, that is it has the power of removing 
oxygen from its combination with metals. This equa- 
tion will illustrate, 

ZnO + C -> Zn + CO. 
4. Proofs for Composition of Diamond. — If heated in 
the absence of air to a dull-red temperature the diamond 
expands considerably, becomes lighter, and turns dark 
in color. If put into a tube, as shown in Fig. 35, with 
the air replaced by oxygen, and heated to bright red- 
ness, the diamond disappears and leaves only an at- 




x - -diamond 

Fig, 35. — Burning of a diamond. 

mosphere of carbon dioxide. A piece of graphite treated 
in the same way gives like results. 

5. Origin of Diamonds. — Some believe that diamonds 
are of meteoric origin and not native to the earth, but 
of this there is little evidence. Undoubtedly they were 
formed under great pressure and a temperature suffi- 
ciently high to render the carbon more or less plas- 
tic, so that crystallization took place upon cooling. The 
great Kimberly mines of South Africa have been thought 
to be the crater of an extinct volcano, and some mines 
discovered in other places seem to be the same. The 
artificial diamonds made by Moissan some years ago 
point to the same theory as probably true. He mixed 
fine iron filings and charcoal made from sugar together, 



162 



APPLIED CHEMISTRY 



put them into an electric furnace made from a block 
of lime, shown in Fig. 36, and by the electric arc melted 
the iron. It is well-known that molten iron will dissolve 
small amounts of carbon. So at this stage, Moissan 
plunged the mass into cold water, whereupon the iron 
solidified upon the outside, and by its contraction pro- 
duced great pressure upon the interior. Thus the dis- 
solved carbon crystallized under sufficient pressure to 
give it the density of the diamond, which is considerably 
above that of graphite. When cool the mass was broken 
up and the iron dissolved in nitric acid, leaving the 
diamonds unaffected. They possessed the hardness and 




Fig. 36. — Moissan's electric furnace. 



other characteristics of native diamonds, but were dark 
in color due to the presence of some uncrystallized par- 
ticles of carbon. The experiment was of scientific in- 
terest, because of the fact indicated that if a source of 
heat sufficient to melt carbon is ever found artificial dia- 
monds will become a possibility. 

6. Uses of Diamonds. — Until it was discovered that 
diamonds could be cut and polished by their own dust, 
they never came into use as ornaments. Imperfect and 
discolored diamonds are used in various ways, because 
of their hardness; for example, in the bearings of fine 



CARBON 163 

watches, delicate balances, for cutting glass, polishing 
other stones, on tips of drills, and other similar ways. 

7. Graphite. — Next to the diamond graphite is the 
most nearly pure form of carbon. It occurs in nature, 
but not in sufficient quantities to meet the demands of 
commerce. Compared with the diamond it has a density 
of only 2.3, diamond being 3.5 ; it is a good conductor 
of electricity, the diamond poor; graphite occurs in six- 
sided plates, the diamond in regular octahedrons; graph- 
ite is a soft, greasy-feeling, black solid, the diamond the 
hardest mineral known, being 10 in the scale, and color- 
less. Since graphite is unaffected by the air it is used to 
give a finished coating to shot and the grains of both 
black and giant powder. It is an ingredient of most 
stove polishes, for the same reason. It is used in cru- 
cibies for melting very refractory substances and to give 
conductivity to wax plates in making electrotypes. 
Mixed with oil it is frequently used as a lubricant for 
bearings of heavy machinery. The most familiar of its 
many uses is in the so-called "lead pencil." This con- 
sists of a mixture of graphite and clay, proportioned 
in such a way as to give varying degrees of hardness 
from very soft to very hard. The clay and graphite 
mixed are moistened with water, made into a soft plia- 
ble mass and by pressure forced through small openings 
in metal plates. When dried these "leads" are ready 
for insertion in the wooden coverings familiar to all. 

8. Coals. — Natural coals are believed to be the meta- 
morphosed remains of the forests of another day. Grow- 
ing at a time possibly when there was more carbon 
dioxide in the air than now, in a climate warm and moist, 
the forests undoubtedly surpassed in luxuriance and 
density anything known upon the earth at the present 
day. Swept down by some groat catastrophe of nature 



164 APPLIED CHEMISTRY 

these forests were buried sufficiently deep to protect 
them from decay through access of the air and at the same 
time to subject them to heat and pressure. Under vary- 
ing conditions of these two factors, a great variety of 
coals was formed, ranging from lignite, brown in color, 
soft, and often showing the original woody structure, 
to anthracite, hard, clean and lustrous. Intermediate 
between these are bituminous coals of great variety, 
rich in oily products, which burn with a yelloAV, smoky 
flame, and semianthracite with most of the bitumen ex- 
pelled, which burns with but little smoke and but 
slightly yellow flame. Cannel coal is very rich in oily 
matter, not suitable for furnaces, but excellent for grate 
fires on account of the freedom with which it burns and 
the abundant yellow flames it gives. Peat is a modern va- 
riety of coal consisting largely of roots only partly 
changed, with the admixture of considerable earthy mat- 
ter. 

9. Petroleum. — From 30 to 40 per cent of some coals 
is an oily product. This may be easily expelled by 
heat. Undoubtedly anthracite and semianthracite coals 
were produced by the greater heat to which they have 
been subjected, which resulted in the volatilization of 
the oily matter. When this took place ages ago, if 
the heat was not so great as to decompose the bitumen 
in the soft coal; it was expelled and found its way into 
layers of sand or other places where it is obtained to- 
day as rock oil or petroleum. Occasionally it is under 
so great a pressure that when opened up it shoots far above 
the surface in a " gusher. ' ' More often it must be pumped 
from the well. Fig 37 shows a number of oil derricks 
with the customary pumps. 

10. By-products of Petroleum. — Petroleum is a black 
or brownish oil of varying density and viscosity, ccm- 



CARBON 



165 



posed of a great variety of carbon compounds. When 
dark in color it is because of particles of free carbon 
contained. There are two general classes of these oils: 
paraffin-~b ase and asphalt-base. These names are given 
for the reason that in the former the thick, less volatile 
portion of the oil is paraffin, while in the latter it is as- 
phaltum. The paraffin oils are regarded as the more de- 
sirable, for the reason that they give on distillation a 
higher percentage of refined products. The asphalt oils 
are regarded by some as of animal origin, instead of veg- 




Fig. '37. — Oil derricks, a familiar sight in oil-producing sections. 

etable, but produced in the same way. When petroleum 
is heated in retorts, the low boiling oils distill over first. 
The process is spoken of as fractional distillation, because 
of the fact that certain portions or fractions coming over 
at a given temperature are separated from other fractions 
obtained at a different temperature. Below 150° C. the 
fraction distilling out is called gasoline; 150° to 300°, ker- 
osene; then successive fractions of heavy burning oil, par- 
affin oil, lubricating oil, vaseline, and paraffin. After the 



166 APPLIED CHEMISTRY 

volatile products are all off from the paraffin oils a con- 
siderable quantity of petroleum coke remains, light and 
porous, which forms a very excellent fuel. These various 
fractions may be still further subdivided if desired. Gas- 
oline may, by taking the portions coming off at smaller 
intervals, be fractionated into petroleum ether, rhigoline, 
benzine, naphtha and gasoline. In fact, it is said that 
some of the refining companies make over one hundred 
products in distilling paraffin-base oils. At present the 
demand made by motor cars and other machines using 
gas engines is mostly for gasoline. Unfortunately, the 
percentage of this in crude oil is not high. Of late years 
the great problem has been to devise some way of convert- 
ing the heavier portions of the oils into the lighter. This 
is called "cracking" and various plans have been sug- 
gested, some of which are fairly successful. Thus a very 
considerable amount of gasoline, although not present 
originally in the oil, may be obtained from most good 
varieties of petroleum. 

11. Natural Gas. — If sawdust or powdered soft coal 
is put into a test tube and heated, not merely is there 
an oily substance, having the odor of tar, driven off, 
but gaseous products as well, which are combustible. 
So, in the earth when the buried forests were being 
subjected to heat, these gaseous products were expelled. 
Probably vast quantities escaped and were lost; other 
portions were caught beneath impervious layers of rock 
and furnish the natural gas of today. Some of it may 
be due to the chemical action of water upon carbides 
that were formed, but this will be considered at another 
time. 

12. Charcoal. — Formerly charcoal was made in the 
characteristic wasteful American way. Great piles of 
wood Avere covered with earth and sod with several 



CARBON 167 

openings at the bottom to allow the entrance of air. The 
wood was then set on fire and the lower portions in 
burning expelled the volatile products from the upper 
portion, forming charcoal. At the present time, with 
our rapidly disappearing forests, the wood in suitable 
lengths is put into iron retorts and heated from beneath 
by means of coal. By this plan not only is a cheaper 
fuel used, but various valuable by-products, such as wood 
alcohol, acetone and acetic acid are saved, with a value 
probably as great as that of the charcoal itself. There is 
great demand also for boneblack, a charcoal made from 
bones. During the last year of the war there was ur- 
gent need also for all the nut charcoal obtainable. This 
is made from cocoanut shells, and all other nuts, even 
from the pits of the peach, apricot and other similar 
fruits. This variety of charcoal is by far the most ab- 
sorptive of any and was used in making gas masks. 

13. Uses for Charcoal. — Besides the special temporary 
use of nut charcoal just mentioned, it has some use at 
all times in research chemical laboratories in absorbing 
and separating small quantities of rare gases such as 
those found in the air belonging to the argon group. 
Boneblack of all the charcoals is probably the most ex- 
tensively used. Its chief value is in refining sugar. The 
syrup, brown in color, is passed through charcoal niters 
whereby the color is removed. A special form of bone- 
black, known as ivory black, made from the horns and 
tusks of animals, is used considerably as a black paint. 
Wood charcoal is sometimes used as a fuel in open fires; 
also in filters for cisterns in suburban and country homes. 
If so used it should be removed at intervals, and heated to 
redness to destroy any organic matter collected within 
the pores. By doing this it is again fit for service. For 
water in a cistern already contaminated a bag of char- 



168 APPLIED CHEMISTRY 

coal suspended in the water for a few days is sometimes 
helpful. 

14. Lamp Black. — This is a finely divided form of car- 
bon obtained by burning in a limited supply of air some 
oil or gas containing carbon and hydrogen. The hydro- 
gen burns, but most of the carbon is deposited as a soot. 
It is the best black paint known when ground in oil. 
It is also the main ingredient of printers' ink. 

15. Coke. — Coke is made by heating coal in iron re- 
torts, as described for making charcoal, or in specially 
constructed ovens. When prepared in retorts the vola- 
tile products are saved and utilized as will be described 
later: from ovens the volatile gases are often allowed 
to escape thus involving great financial loss, as fully 
one-fourth the fuel value is contained in the volatile 
portions. Coke is a dark, or steel-gray, porous solid, 
which burns with intense heat. It is used in iron and 
other smelters because of its fuel and reducing values. 

16. Gas Carbon.— On the interior of retorts used in 
making coke a fine-grained form of carbon is slowly 
deposited. At intervals this is removed, molded into 
sticks and plates, and used in arc lights, battery plates 
and similar other electrical work. 

17. Carbon Monoxide. — Carbon forms two oxides, the 
monoxide, CO, and the dioxide, C0 2 . The latter is al- 
ways produced in the combustion of carbon when the 
supply of oxygen is plentiful ; when insufficient the for- 
mer is the result. Little thought is usually given to the 
low^er oxide, but on account of its poisonous properties 
it demands a very careful study. It may find access to 
the home in various Avays. Most modern houses are 
heated by hot-air furnaces, usually made of cast iron. 
Fig. 38 shows the construction. The air enters freely 
through the ash-pit and in the lower portions of the 



CARBON 



169 



firebox carbon dioxide is produced. As this passes up 
through the layers of red-hot carbon, where there is no 
air, carbon monoxide is formed, thus, 

C0 2 + C -> 2CO. 

Then as the monoxide flows into the space above the 
fire it again meets oxygen entering through the drafts 
and about the door. Hence, it burns and forms carbon 
dioxide again, thus, 

2CO + Oo -» 2COo. 




Fig. 38. — Formation of carbon monoxide in a furnace. 

The nickering blue flames of burning carbon monoxide 
may plainly be seen in a furnace into which no coal 
has been thrown for some time. Likewise, most of the 
time it may be seen in base burners which use hard 
coal. Under conditions, as just described, no carbon 
monoxide remains and the products of combustion are 
carried out through the fine to the air. There are times, 
however, when this is not true. Ai night, in banking the 
fire so that it will keep well till morning, usually con- 



170 APPLIED CHEMISTRY 

siderable coal is put into the firebox. Now, when the 
carbon monoxide formed in the interior of the fire 
reaches the open space, it has been cooled by the layer 
of coal on top to such an extent that it does not burn. 
It is then occluded or absorbed by the hot iron of the 
furnace as is hydrogen by platinum or palladium. 
Quickly it passes through to the air space about the fur- 
nace and is carried by the ascending currents into the 
living rooms above. The same thing occurs with base 
burners when the coal is shaken down in considerable 
quantities from the reservoir above. Gas heaters, when 
improperly regulated, as may be known by the flame 
being yellow, often produce carbon monoxide, and to- 
bacco smoke always contains a considerable quantity 
of the poisonous gas. In lighting with gas, if the man- 
tle is being blackened by a deposit of soot, carbon mon- 
oxide is invariably being formed ; a cook stove, burning 
with a yellow flame, is not receiving sufficient air for 
perfect combustion, and in all probability is producing 
some carbon monoxide. The burned gases from a motor 
car or other similar gas engine, especially if the engine 
is running "idle," contain considerable quantities of 
carbon monoxide. 

18. Characteristics of Carbon Monoxide. — It is a col- 
orless gas, of nearly the same density as air. It has a 
peculiar, somewhat disagreeable but very faint odor. It 
may be liquefied at -190° C. It burns with a pale blue 
flame, producing carbon dioxide. From this fact, that 
it is able to take up more oxygen, it is a reducing 
agent and often serves thus in the separation of metals 
from their oxides. This is notably the case with iron, 
shown by the equation, 

Fe 2 3 + 3CO -> 2Fe + 3C0 2 . 



CARBON 171 

Carbon monoxide is very poisonous. When inhaled it 
forms a compound with the hemoglobin which prevents 
the carrying of oxygen to the tissues. Thus even in 
moderate amounts, it causes serious results, asphyxiation 
and death. Most fatalities reported from asphyxiation 
by the exhaust from motor cars in a closed garage are 
due to the poisonous effects of carbon monoxide. Years 
ago, in the warmer countries of Europe, open charcoal 
fires were the common method of heating the homes, 
and many cases of death, accidental or otherwise, are on 
record due to putting considerable charcoal on top of 
the fire and retiring. Knowing the poisonous charac- 
ter of the gas no one should sleep in a room warmed by 
a furnace with the register left open, and even thus, 
the windows should be raised. In the case of other 
sources of the gas, as already mentioned, steps should 
be taken at once to remove the cause. Following ex- 
plosions in coal mines, quantities of carbon monoxide 
exist, called by the miners "after damp" or "black 
damp." Usually it is the cause of the greater number 
of fatalities. 

19. Carbon Dioxide. — This gas has already been men- 
tioned as a constituent of the air. It results from the 
decomposition of organic matter, from combustion and 
from respiration. All of these sources furnish very con- 
siderable amounts, but the proportion of three or four 
parts per ten thousand of air remains practically con- 
stant, due to the action of plant life. 

20. Preparation. — Carbon dioxide in the laboratory or 
for commercial purposes is usually obtained by the re- 
action of some carbonate, as limestone or marble, with 
an acid, generally hydrochloric. The equation is 

CaC0 3 + 2HCl -» C0 2 + H 2 + CaCl 2 . 



172 APPLIED CHEMISTRY 

It may be collected either by downward displacement 
or over water; for commerce it is compressed in steel 
cylinders. 

21. Characteristics. — Carbon dioxide is a colorless, 
odorless gas with a density about once and a half that of 
the air. This may be shown by pouring the gas from 
a wide-mouthed liter bottle into the upper end of a 
trough in which are some short burning candles as 
shown in Fig. 39. The gas cannot be seen, but one 
candle after another is extinguished as the carbon di- 
oxide flows down. A liter bottle is usually sufficient to 
make the experiment three times in succession. The gas 




Fig. 39. — Pouring carbon dioxide upon burning candles in a trough. 

is soluble in water, about volume for volume at ordi- 
nary temperatures. At -79° C. it may be liquefied; if 
the liquid be allowed to escape rapidly, the lowering of 
temperature caused by the evaporation converts a con- 
siderable amount of the liquid into a white solid, resem- 
bling snow, which vaporizes without melting, just as io- 
dine crystals do. Mixed Avith ether, solid carbon dioxide 
is often used as a freezing mixture ; with it mercury 
may be easily solidified and many other interesting ex- 
periments performed. Carbon dioxide will not burn 
and is so stable that with very few exceptions it cannot 



CARBON 173 

be decomposed by a burning metal. Magnesium rib- 
bon, ignited and thrust into a bottle of the gas, con- 
tinues to burn with the formation of magnesium oxide 
and free carbon. Both products, being solids, may be 
seen upon the sides of the bottle. The equation illus- 
trating the action is 

2Mg + C0 2 -» C + 2MgO. 
When dissolved in water some portion of the gas reacts 
chemically, forming a weak and unstable acid, thus, 

C0 2 + H 2 *=* H 2 C0 3 . 

Under pressure, carbon dioxide obeys Henry's law, that 
the amount of gas dissolved by a liquid is proportional to 
the pressure. That is, at five atmospheres' pressure a liter 
of water would dissolve five times as much gas as at one 
atmosphere. 

22. Uses. — The purpose of the small amount of carbon 
dioxide in the air has already been mentioned. Soda 
water, so called, is familiar to all. It is water charged 
with the gas under two or three atmospheres' pressure; 
as soon as this is relieved the gas begins to escape with 
the familiar effervescence. Most soft drinks in bottled 
form are thus carbonated. Carbon dioxide, liquefied in 
tiny steel capsules, called " sparklets," may be had from 
the supply houses. They are to be used for the carbon- 
ation of water either at home or in camp; for this a 
specially designed apparatus is necessary, which alloAvs 
the escape of the gas into the bottle of water by piercing 
the cap with a stiff needle. Two sizes are made, suffi- 
cient for the carbonation of a pint or a quart of water. 
The chemical fire extinguisher, seen often in the hall- 
ways of public buildings, and larger sizes upon fire 
trucks, makes use of carbon dioxide. Fig. 40 gives a 
sectional view. Water is put into the vessel, made of 



174 



APPLIED CHEMISTRY 



copper or brass, up to the shoulder ; in this a pound or a 
pound and a half of baking soda is dissolved. In the 
tank near the top supported in a wire frame is a bottle 
partially filled with sulphuric acid. The stopper of this 
bottle fits very loosely so that it readily drops out if in- 
verted. For use the whole apparatus is turned upside 
down; the acid flows out into the soda solution, and 
reacting* with the bicarbonate generates carbon dioxide 



yi4 

e 



Fig. 40. — Babcock fire extinguisher. 



rapidly: the pressure thus obtained throws the water 
charged with gas upon the fire. The reaction is shown 
by the equation, 

NaHC0 3 + H 2 S0 4 -* C0 2 + H 2 + NaHS0 4 . 
The effect of carbon dioxide may be illustrated by a lit- 
tle experiment upon the lecture table. A small evap- 



CARBON 175 

orating dish partly filled with gasoline is ignited; it 
may be instantly extinguished by pouring carbon di- 
oxide from a wide mouthed liter bottle. Usually a liter 
of gas is sufficient to repeat the experiment twice. 

23. The Test for Carbon Dioxide. — On account of its 
density carbon dioxide often collects in old, long-unused 
wells and shafts. Although it is not poisonous, one may 
drown in it as quickly as in water. It is necessary, 
therefore, to test the air before entering places where 
it may have accumulated. This may be done by lower- 
ing a lantern : if it continues to burn well, the air is 
safe to breathe. In the laboratory carbon dioxide is 
tested by bubbling it into lime water, with which it 
forms a milky white precipitate. If the operation be 
long continued the precipitate redissolves, thus, 

Ca(HO) 2 + C0 2 -^ CaC0 3 + H 2 0. 

The white precipitate is calcium carbonate 

CaC0 3 + H 2 + C0 2 -^ CaH 2 (C0 3 ) 2 . 

The product formed by the continued action is acid cal- 
cium carbonate which is soluble in water, hence the ex- 
planation of the disappearance of the precipitate. 

24. Other Carbon Compounds. — Carbon tetrachloride, 
as the name would indicate, has the formula, CC1 4 . It is 
a slightly yellow, oily liquid, heavier than water, not in- 
flammable, an excellent solvent for oils and grease, and 
at present not very expensive. It may, therefore, be 
used instead of gasoline with perfect safety for cleaning 
garments. "Carbona," a largely advertised cleaning 
compound, is mostly carbon tetrachloride. While it 
contains some benzine there is not sufficient quantity 
to render the mixture inflammable. "Pyrene," a well- 
known fire extinguisher, frequently carried by motor 
car owners in small cylinders, is largely carbon tetra- 



176 APPLIED CHEMISTRY 

chloride. It is readily vaporized, and as the gas is heavy 
and not inflammable it extinguishes the fire by shutting 
off the oxygen supply. Silicon carbide. SiC, made by 
fusing in an electric furnace a mixture of sand and coke 
with common salt, is a crystalline solid of a dark gray 
or purple color. The reaction is shown thus, 

Si0 2 + 3C->2CO + SiC. 
The compound is said to be even a shade harder than 
the diamond and is used extensively under the name. 
carborundum, as an abrasive. It is made into whetstones, 
wheels, and a great variety of other forms for cutting and 
polishing. Another very valuable carbide is made by fus- 
ing in an electric furnace a mixture of lime and coke. thus. 

CaO-3C -> CaC 2 -CO. 

It is known as calcium carbide and is used extensively as 
mentioned elsewhere for the preparation of acetylene. 

Exercises for Review 

1. What can you say of the importance and. total quantity of 
carbon in nature? Xame some of the many forms in which it oc- 
curs, as compounds. 

2. Classify the forms of carbon. 

3. Give proof that the diamond is carbon. 

4. Give an account of Moissan 's experiment in making diamonds. 

5. Give the chief characteristics and practical uses of the dia- 
mond. 

0. Compare grapMte with diamond. Give several important uses. 
7. Classify the coals. "What is their c rig-in ? Why so different? 
v . What is the origin of petroleum? Xame two kinds. Win- 
so called? 

9. What is fractional distillation? What use is made of it? 
What is meant by "cracking' - an oil? 

10. Xame some of the valuable products obtained from petro- 
leum. 

11. What is the probable origin of natural gas? 

12. How is charcoal made and what by-products are obtained? 



CARBON 177 

13. Name several varieties of charcoal and give uses of each. 

14. What is ivory black? Lamp black? Uses of each? 

15. How is coke prepared? Its chief uses? 

16. What is the source of gas carbon? What uses has it? 

17. Name several ways in which carbon monoxide may find its 
way into the home, Give the details of one case. 

18. Describe carbon monoxide. Its effects upon the blood. 

19. Give the sources of carbon dioxide in the air. 

20. How is carbon dioxide made for commerce? Equation. 

21. Give chief properties of carbon dioxide. 

22. Name some important uses for carbon dioxide. 

23. Describe the chemical fire extinguisher. Give the chemical 
reaction. 

24. Give two tests for carbon dioxide. 

25. What valuable uses has carbon tetrachloride? Name some 
commercial forms in which it appears. 

26. Name two carbides, state how made and uses of them. 



CHAPTER XIII 

VALENCE 
Outline — 

Meaning of Valence 
Degrees of Valence 
Valence of Radicals 
Variation of Valence 

Saturated and Unsaturated Compounds 
Valence in Ternary Compounds 

1. Meaning of Term. — As used in chemistry the term 
valence means the power an atom has of combining with 
one atomic weight of hydrogen or its equivalent. Thus, in 
hydrogen chloride, one atomic weight of chlorine combines 
with one of hydrogen. As the hydrogen atom serves as 
the unit, chlorine must have a valence of one ; likewise, 
do bromine, fluorine and iodine. Radicals, not being com- 
pounds but groups serving like atoms, as parts of a com- 
pound, likewise have valence. Thus, chloric acid, HC10 3 , 
shows that the group -C10 3 has a valence of one ; so, also, 
ammonium, NH 4 -, in ammonium chloride; -N0 3 in ni- 
tric acid; -HO in sodium hydroxide and several others. 
As the metals are electropositive and do not form any 
familiar compounds with hydrogen, their valence must 
be determined by examining some such compound as 
their chlorides. Thus, common salt, NaCI, shows that so- 
dium has a valence of one ; KC1, that potassium has a val- 
ence of one. All atoms or groups having a valence of one 
are said to be univalent or are sometimes called monads. 

2. Valence Greater than One. — If we examine the for- 
mula for the water molecule, we see that oxygen has 
combined with two atoms of hydrogen, hence oxygen is 

178 



VALENCE 179 

said to have a valence of two. Similarly, magnesium as 
seen in magnesium oxide, MgO, copper in copper oxide, 
CuO, calcium in lime, CaO, all have a valence of two 
and are called bivalent or diads. Aluminum and iron 
as shown by the formulas, A1C1 3 and FeCl 3 , are trivalent 
or triads; while carbon, as seen in carbon dioxide or car- 
bon tetrachloride, and silicon in silicon dioxide, Si0 2 , are 
tetrads or quadrivalent. Phosphorus as seen in the com- 
pounds P 2 5 and arsenic in As 2 5 are pentads. 

3. Radicals of Valence Higher than One. — In sul- 
phuric acid, H 2 S0 4 , sodium carbonate, Na 2 C0 3 , and po- 
tassium chromate, K 2 Cr0 4 , are seen radicals combining 
with two univalent atoms ; hence, -S0 4 , -Cr0 4 and -C0 3 
must be bivalent. Likewise, -P0 4 and -B0 3 , seen in the 
phosphoric and boric acids, H 3 P0 4 and H 3 B0 3 , are tri- 
valent; while -Si0 4 found in orthosilicic acid, H 4 Si0 4 , 
is quadrivalent. 

4. Variation in Valence. — Nitrogen and phosphorus 
are spoken of above as being quinquivalent. Their ox- 
ides indicate this. But they also form the hydrogen 
compounds, ammonia, NH 3 , and phosphine, PH 3 , in 
which a valence of three is indicated. In another chap- 
ter, copper is seen to form two compounds, as also mer- 
cury, CuO and Cu 2 0, HgCl 2 and Hg 2 Cl 2 , indicating 
sometimes a valence of one, sometimes of two. Many 
other cases might be cited, notably carbon in carbon 
monoxide and the dioxide, also marsh gas, CH 4 , and 
ethylene, C 2 H 4 . In the case of the carbon atom the va- 
lence is universally regarded as four and such compounds 
as ethylene, C 2 H 4 , acetylene, C 2 H 2 , and the monoxide 
are said to be unsaturated. By this is meant that the 
carbon atom in such compounds has not combined with all 
that it is capable of holding. There is abundant evidence 
that this is true. We have seen already in the case of the 



180 APPLIED CHEMISTRY 

carbon monoxide that it readily combines with another 
atom of oxygen forming the dioxide; also, that inhaled it 
completes the saturation by combining with the hemoglo- 
bin of the blood ; likewise, it readily unites with two atoms 
of chlorine to form phosgene, COCl 2 . Other very re- 
markable and interesting proofs for the carbon com- 
pounds are abundant. One of these is the passage of the 
gas through a solution of bromine in water or through 
a quantity of bromine beneath a layer of water to prevent 
its escape into the air. Marsh gas, CH 4 , if carbon has a 
valence of four, would be a saturated compound. When 
it is slowly bubbled through bromine, no matter how long 
continued, the escaping gas has all the properties of 
marsh gas and the bromine remains unchanged. On the 
other hand, if ethylene, C 2 H 4 , be used in the same way, 
the bubbles in passing through seem to become smaller 
as if they were being absorbed, and after an hour or two, 
the red color of the bromine has entirely disappeared, 
and in its place is a colorless, oily liquid, of pleasant odor, 
without the slightest resemblance to bromine. An analy- 
sis of this liquid shows that it contains two atomic 
weights of bromine per molecule, as would be represented 
by the formula, C 2 H 4 Br 2 . If written graphically, which 
shows the structure or arrangement, marsh gas is 

H H H 

I I I 

H-C-H, ethylene, -C-C-, and the bromine compound, 

H H H 

H H 

I I 
Br-C-C-Br. These formulas show that in marsh gas, the 
I I 
H H 

carbon atom has all its bonds saturated with hydrogen: 
that in ethylene there are two not so used and it is to 



VALENCE 181 

these that the bromine has been attached. A very large 
number of other similar experiments have been made, 
all of which seem to show the truth of the position taken. 
Likewise, in the case of most of the seeming variations in 
valence, one or more of the compounds are unsaturated 
ones. Thus nitrogen in ammonia, NH 3 , seems to have a 
valence of three ; but ammonia readily forms additional 
compounds, as when it is brought into contact with hydro- 
chloric acid, thus, 

NH 3 + HC1 -> NH 4 C1. 

In the last compound the nitrogen atom is combined with 
five univalent atoms. Likewise, ammonia combines addi- 
tively with nitric acid, 

NH 3 + HN0 3 ^NH 4 N0 3 , 

in which compound the nitrogen atom is combined with 
four univalent atoms and one univalent group. Mercury 
in mercurous chloride, Hg 2 Cl 2 has apparently a valence of 
one, while in mercuric chloride, HgCL, it is evidently two. 
In all probability the mercury atom always has a valence 
of two, and any compounds not indicating such are unsat- 
urated. It is well known that mercurous salts readily 
take up more of an electronegative element or group 
and become mercuric compounds. Thus, many other 
cases might be considered but for the present these seem 
sufficient. 

5. Ternary Compounds. — Sometimes it becomes de- 
sirable to determine the valence of an element in a com- 
pound, knowing the formula. In binary compounds, 
if the valence of one of the elements is known, the 
other is evident at a glance. In ternary compounds 
this is not true. However, if it is known that the valence 
of the oxygen atoms is equivalent to the added valences 
of the other atoms present, it becomes easy. To illus- 



182 APPLIED CHEMISTRY 

trate, sulphuric acid has the formula. H 2 S0 4 . It is de- 
sired to know the valence of the sulphur atom in the 
compound. There are four oxygen atoms whose total 
valence is 8: the two hydrogen atoms have a valence 
of 2 ; hence. 2+ S ==' 8, from which sulphur must be 6. 
In potassium diehromate. K 2 Cr 2 7 , the equation, 2 - 2Cr 
= 14, indicates the several valences, from which chro- 
mium is found to be six. 

Exercises for Review 

1. Define and illustrate valence. 

2. Name some elements with a valence of one : some radicals 
with the same valence. 

3. Xame some elements with valence of two : also some radicals. 

4. What names are given to elements with valence of one, two, 
three, etc. ? 

5. What is meant by an unsaturated compound? Xanie two. 

6. Give some experimental proof that ethylene is unsaturated, 

7. What facts indicate that carbon monoxide is unsaturated? 

S. What is a structural or graphic formula? What advantage 
has it? 

9. What evidence is there that ammonia is unsaturated? 

10. Find the valence of chromium in KX , r0 4 : nitrogen in HX0 3 : 
manganese in KMn0 4 : iron in Fe,0 3 : phosphorus in P,0 5 ; phos- 
phorus in H 3 P0 4 . 



CHAPTER XIV 

ILLUMINATING AND FUEL GASES 

Outline— 

Natural Gas 
Acetylene 
Pintsch Gas 
Blau Gas 
Coal Gas 
Water Gas 

1. Natural Gas. — This lias already been mentioned 
and its supposed origin. Another theory has been sug- 
gested by some which may possibly account for at least 
a part of the natural supply. Two carbides have been 
mentioned in the preceding chapter. One of them re- 
acts with water, as will be seen, to form a combustible 
gas. Another, aluminum carbide, does likewise. It is 
thought that at some time in the past this carbide has 
been formed in the earth and that Avater coming in 
contact with it reacts forming marsh gas, which is the 
main constituent of natural gas. The reaction with 
water is here shown, 

Al 4 C 3 + l2H 2 _* 3CH 4 + 2A1 2 (H0) 6 . 

2. Acetylene. — For commercial purposes, acetylene is 
always prepared by the reaction of water upon calcium 
carbide, thus, 

CaC 2 + 2H 2 -^ C 2 H 2 + Ca(HO) 2 . 

Owing to the high percentage of carbon in the gas, it 
cannot be used in an ordinary burner, for the insuffi- 
cient amount of air supplied results in a very smoky 
flame. A special tip, shown in Fig. 41, is designed so 

183 



184 APPLIED CHEMISTRY 

as to draw in the air by two minute jets of gas directed 
toward each other. Burned thus, a brilliant white light 
is obtained with only about one-fifth the quantity of gas 
consumed as in other common burners. It is thus used 
extensiYely in motor cycles : for this purpose it is con- 
tained in the familiar "Prestolite" tank. At first, at- 
tempts were made to use acetylene in liquefied form, 
but it was found under such pressures to be readily 
explosive and many accidents occurred. It is very solu- 
ble in acetone, a liquid of pleasing odor obtained in 
the destructive distillation of wood in making charcoal. 
The prestolite tank applies this principle : large quan- 




Fig. 41. — Acetylene burner. 

tities of acetylene under several atmospheres pressure 
are dissolved in the acetone in the tank and in this form 
it is perfectly safe. On use the gas escapes, but the 
acetone remains and may be recharged. For cooking 
purposes special plans must be had for furnishing in- 
creased quantities of air, otherwise the cooking vessels 
become heavily coated with soot. At the present time 
acetylene is used extensively in country churches and 
suburban homes both for lighting and cooking. There 
are several types of generators, but the most satisfac- 
tory is one in which the carbide in coarse grains drops 
slowly into a considerable quantity of water. The gas 



ILLUMINATING AND FUEL GASES 185 

is piped throughout the house in the usual way and 
burned in tips like the one described above. The most 
valuable use of acetylene at the present time is for 
welding and similar work where great heat is required. 
The gas is used in a torch such as was described for oxy- 
hydrogen work, and when properly adjusted burns with 
a pale blue, intensely hot name. Even when air in- 
stead of oxygen is used, furnished with a foot bellows, 
iron wire, such as is used in baling hay, may be burned 
rapidly in the air with a beautiful and dazzling shower 
of sparks. In welding, the broken object is heated, the 
crack made somewhat larger; then a rod of steel is 
melted in the oxyacetylene flame and the molten steel 
allowed to flow down into the crack. Welding thus 
properly done is said to make the object as strong as 
at the beginning. 

3. Pintsch Gas. — This gas received its name from an 
Englishman who first prepared it for the purpose of 
lighting the stage coaches of that day. At the present 
time it is used practically nowhere outside railway 
coaches, where it is seen in clusters, usually enclosed in 
glass globes at the ceiling. It is prepared from some 
oil, often naphtha, by heating sufficiently high to decom- 
pose it into gases which will not liquefy again upon 
cooling. As it is thus made from a refined oil, the re- 
sulting gas needs little purification, other than the re- 
moval of a little tar and water. It is carried, heavily com- 
pressed, in cylinders under the railway coaches. Unlike 
most similar gases, the compression does not greatly re- 
duce its illuminating powers. 

4. Blau Gas. — At the present time a similar gas, called 
Blau gas, is being manufactured from a less refined oil 
than the pintsch uses. It is purified and compressed. 
whereupon some of the constituents become liquid. 



186 APPLIED CHEMISTRY 

These are removed and the gas is then stored in steel 
cylinders under high pressure. In the oxyhydrogen 
blowpipe it gives intense heat ; it is also used in subur- 
ban homes for cooking and lighting purposes as other 
gases are in the city. For such use two tanks of the 
compressed gas are placed in a container outside the 
building and attached to the piping of the house. When 
one is exhausted it is sent to the factory for refilling and 
the other put in service. 

5. Coal Gas. — Most cities in sections where bitumi- 
nous coals are to be had, use large quantities of coal 
gas. It is prepared by heating the soft coal in iron 
retorts as already mentioned for making coke. The 
resulting gaseous mixture, very impure, must be puri- 
fied before being suitable for use. By cooling, first the 
tar is removed and flows into a tank or well fitted to re- 
ceive it. The gas next passes through, usually, two 
"towers," filled with lumps of coke or something equiv- 
alent, kept moist by water trickling over it. Here the 
ammonia is removed. The gas next passes through 
three or four purifiers, containing lime or ferric oxide, 
which remove other compounds like sulphur dioxide, 
hydrogen sulphide and carbon dioxide, all acidic in 
character and either not combustible or very undesir- 
able in an illuminating gas. Finally, the gas is metered 
and passed into a storage tank from which it is piped 
to all parts of the city. Remembering that coke and 
gas carbon are both obtained in the retorts it will be 
seen that there are four by-products of the manufacture 
of coal gas. Besides the two just named, are the tar 
and ammonia. Tar is a black, viscous, ill-smelling liquid 
consisting of a mixture of a great variety of compounds 
and black because of the presence of some free carbon. 
From it are made several colorless liquids, such as 






ILLUMINATING AND FUEL GASES 187 

aniline and toluol. These form the basis of an indefi- 
nite number of other compounds of the very greatest 
value: photographic developers, such as hydroquinon; 
many medicines, like aspirin; all the great variety of 
beautiful aniline dyes; phenol or carbolic acid and its 
many derivatives ; picric acid and the explosives from 
it; the explosives from toluol, and hundreds of others. 

A ton of coal will make about ten thousand cubic 
feet of gas containing one-fourth to one-third the fuel 
value of the original coal. The gas consists of hydro- 
gen and marsh gas, over 40 per cent of each, with carbon 
monoxide, and ethylene as the greater part of the bal- 
ance. Small proportions of some higher hydrocarbons 
are usually present. 

6. Water Gas. — This receives its name from the fact 
that steam is used in its preparation. Often both coal 
and water gas are manufactured simultaneously in the 
same building. The coke obtained as a by-product in 
the coal gas department is withdrawn red-hot from the 
retorts into small steel cars in which it is carried quickly 
to another part of the building. Here it is dumped 
through a trap door into a vertical, cylindrical retort 
on the floor below. A blast of air is turned on the hot 
coke to raise its temperature, and then live steam is 
passed through it, when the following reaction takes 
place, 

H 2 + C -> H 2 + CO. 

At the end of about three minutes the temperature is 
too low to effect the decomposition of the steam, which 
then, automatically, is cut off and the air again turned 
on. Thus, in three minute periods, mechanically, all 
day the steam and air are turned on alternately, with 
results as shown by the equation. Both the constitu- 
ents thus obtained are combustible, but a gas richer in 



188 APPLIED CHEMISTRY 

carbon is more desirable. Hence, it is passed through 
another retort containing a lattice work of fire brick 
heated to redness by a gaseous fuel. Into this cham- 
ber is sprayed an oil obtained from petroleum, which 
is decomposed as was described in making pintsch 
gas. These products are mixed with the two already 
obtained from the steam and coke, such that the final 
result is not essentially different from coal gas. The 
percentage of carbon monoxide is higher, hence the gas 
is more poisonous. In factories making both coal and 
water gas the large storage tank receives both usually 
in something like the proportion of 3 of water to two 
of coal gas. In other cities where cheap supplies of soft 
coal are not available, as in California, a gas is prepared 
from crude petroleum, not essentially different from the 
coal gas, and of excellent quality. 

Exercises for Review 

1. Give a chemical theory for the formation of natural gas. Of 
what does natural gas consist? 

2. How is acetylene made? Write the equation. Describe the 
tip necessary for burning it successfully. 

3. Describe the prestolite system of lighting. 

4. Why not use liquefied acetylene for lighting? 

5. Give some important uses of acetylene. 

6. How is pintsch gas made? Where is it used? 

7. How is blau gas made? For what used? 

8. Describe the process of making coal gas. Name the impuri- 
ties removed in its manufacture; also the by-products obtained. 

'9. How is the ammonia recovered and purified? 

10. What are some of the products obtained from tar? 

11. What are gas carbon and coke used for? 

12. Describe the preparation of water gas. Why is it so called? 

13. How is the composition of water gas different from that of 
coal gas? 

11. Write the equation showing the effect of the hot coke on the 
steam. 

15. What is meant by "live" steam? 



CHAPTER XV 

FLAME 
Outline — 

Definition of Flame 
Chemical Eeaction in a Flame 
Structure of Flames 
The Bunsen Burner 
Applications in the Home 
The Oxyhydrogen Blowpipe 
The Blast Lamp 

1. What is a Flame? — Briefly stated, a flame is usu- 
ally said to be a burning gas. It is the phenomenon 
which accompanies the rapid union of two gases, produc- 
ing heat and usually light also. At first thought this 
might not seem to be always true. In the case of a 
burning gas jet there could be no question about it. The 
gas, being heated to the kindling temperature, begins to 
combine with the oxygen of, the air; this chemical union 
is productive of heat and a temperature above that nec- 
essary for the kindling of the gas is constantly maintained. 
With a candle it is equally true. The wick is filled 
with wax. When a burning match is applied to it, first 
the wax is melted, then it begins to vaporize and the 
gas thus formed is ignited. Thereafter, the heat of the 
chemical union is such as to vaporize continuously the 
paraffin with a steady flow of gas. By quickly blowing- 
out the flame of the candle, the paraffin vapors may 
be seen floating upward and may easily be ignited with- 
out touching the wick. When this is done the flame 
rapidly passes down the stream of gas to the wick. Ex- 
actly the same thing is true of the kerosene or alcohol 
lamp. Likewise, when wood is burning the heat of 

189 



190 APPLIED CHEMISTRY 

combustion decomposes the cellulose and other com- 
pounds present, converting much of them into gaseous 
form. These escape in tiny streams here and there and 
combining with the oxygen produce flames. It is the 
same with soft coal. The oil contained, by means of the 
kindling used, is first partially volatilized ; later, by the 
heat of combustion not only does volatilization continue 
but also decomposition of the vapors into hydrocarbon 
gases, all of which are combustible. Charcoal, coke and 
anthracite coal contain little or no volatile matter; 
hence, they burn without flame. It is true that often 
light blue lambent flames may be seen above the surface 
of such fires, but these are due to the carbon monoxide, 
produced in the interior of the burning mass through 
the interaction of the carbon dioxide and red-hot carbon. 
This has been explained elsewhere. It must be con- 
cluded, therefore, that whenever there is flame, there is 
a gas present. 

2. The Chemical Action. — Combustion is sometimes 
spoken of as the rapid union of oxygen and some other 
substance. This is a narrow view. A flame may accom- 
pany the union of a variety of substances, and in each 
particular case, one of the substances is as essential as 
the other. For example, an ignited jet of hydrogen, 
thrust into a bottle of chlorine, continues to burn as vig- 
orously as in the air. Likewise, if an inverted bottle of 
hydrogen be ignited at the mouth and a jet of chlorine be 
introduced through the flame into the bottle, the chlorine 
will be seen to burn. In this case combustion is the rapid 
union of the hydrogen and chlorine, and it makes little 
difference which is introduced into the other; one is just 
as essential as the other. In the same way a stream of 
air, or oxygen, passed through the flame into the bottle 
of hydrogen continues to burn just as well as the jet of 



FLAME 191 

hydrogen does in the air. This is illustrated by a com- 
mon, simple experiment. The smaller tube in Fig. 42, 
marked ' ' gas, ' ' is attached to the gas supply. The larger, 
short tube is open to the air. When the gas has been flow- 
ing sufficiently long to expel all the air a small flame 
brought to the upper end of the ' ' air ' ' tube will apparently 
ignite the air current and it will continue to burn. Here 
the combustion is the union of the gas and oxygen and 
the flame occurs at the place where this union is going 
on. 




Fig. 42. — "Burning" air. 

3. Structure of a Flame. — The ordinary flame of 
which that given by a candle is typical consists of three 
portions, or concentric cones. A few simple experiments 
readily enable one to determine the condition of each 
of these portions. A pine splint held across the flame 
of a large candle, or more conveniently, a small Bunsen 
burner flame, will be scorched in two places, at the 
points where it intersects with the circumference of the 
flame. If a sheet of paper be pressed down upon a 
small Bunsen flame, or better, if the burner be inverted 
and held close to the paper lying on the table, it will 
be scorched in a circle, agreeing with the circumfer- 
ence of the flame. These would indicate that the burn- 



192 



APPLIED CHEMISTRY 



ing portion of the flame is at the outer edge. To show 
this more strongly, a match may be thrust through the 
outer zone and held until the wood begins to burn at 
the circumference of the flame without the more com- 
bustible material of the head of the match being ignited 
at all. This may be varied by turning off the gas and 
suspending a match in the burner by means of a pin 
thrust through the wood a half inch or so from the head. 
If now the gas is turned on and ignited at some dis- 
tance above the tip, it will burn as usual while the match 
remains unaffected at the center. These experiments 




Fig. 43. — Match suspended within burning gas jet. 



show that there is no heat in this innermost cone ; lastly, 
a small tube inserted into this section and held at an an- 
gle, may be lit at the upper end. This shows that this 
portion contains unburned gas. The same experiments 
may be carried out with a large candle. (See Fig. 44.) 
Inspection of a Bunsen flame with the openings near 
the bottom closed or of the candle flame shows that the 
middle cone is yellow. Around this is an outer blue 
cone, very thin at the base, much larger in the upper 
part. A cold dish held against the yellow portion is 



FLAME 



193 



soon covered with soot which we know is a deposit of 
carbon. It is the myriads of carbon particles floating 
in this zone and heated to incandescence, that is to a 
temperature at which they will glow, which give the 
light. It may be concluded then that this middle cone 
consists of gas undergoing combustion but not com- 
pleted and contains much incandescent carbon. The 
outer cone gives little or no light. In the daytime it 
looks much smaller than it really is. A pine splint ap- 




Fig. 44. — Burning gas drawn from center of candle flame. 

proached slowly from above or from the side ignites 
long before it touches any visible flame. This is evi- 
dently the hot portion and is the zone of complete or 
perfect combustion: In it the carbon is burned to carbon 
dioxide and the hydrogen to vapor. Obviously, if heat 
is desired as in softening a glass rod, it will be secured 
in the upper, nearly invisible, blue portion of the flame. 
If reducing action is wanted, since red-hot carbon has 



194 APPLIED CHEMISTRY 

such power, it will be had in the yellow eone. A penny 
held in the tip of the flame becomes black from a coating 
of copper oxide ; held in the yellow portion it becomes 
bright again because the hot carbon removes the oxygen 
from the film of oxide. 

4. The Bunsen Burner. — There are several types of 
this burner found in laboratories. In all of them the 
gas enters through a very small opening somewhere 
near the bottom, and all have some arrangement for 
introducing considerable air somewhere near where the 
gas enters, so that the two become mixed before leav- 
ing the tube. The result is that if properly adjusted 
there are only two portions to such a flame. The lu- 
minous part has disappeared, w T hile the outer cone is 
much enlarged. There is thus obtained a hotter flame 
than is possible otherwise. By opening and closing the 
air vents at the bottom it will be seen that the flame is 
much shorter when the air is on than otherwise ; hence 
all the heat of the combustion is concentrated within a 
shorter portion than when the air is not entering. Some- 
times, in such burners, if the gas pressure is low, the 
burner "strikes back" and continues to burn near the 
base. In this case the rate of combustion or speed of 
propagation of the flame has been more rapid than the 
flow of gas, and the flame is passed down the pipe to 
the point of exit of the gas. Owing to the lack of air 
needed for perfect combustion, acetylene and other 
offensive gases are often produced in such cases and the 
difficulty should be speedily remedied. Usually by turn- 
ing off the gas and lessening the air supply the burner 
may be relit successfully. 

5. Applications in the Home. — Every gas stove used 
for cooking and, as a rule, for heating as well, employs 
the principle of the Bunsen burner. There is some de- 



FLAME 195 

vice for admitting a supply of air and mixing it with 
the gas before it reaches the burner where it is to be 
consumed. If properly adjusted, the flame will be blue 
and relatively hot. A yellow flame indicates that not 
sufficient air is being provided; hence results will be 
slow and unsatisfactory. Sometimes the burners on a 
stove, especially the oven, may strike back and burn at 
the point of admixture of the gas and air. This is espe- 
cially apt to occur after the oven has been burning for 
some time and the pipes have become hot. The cause is 
the same as in the case of the Bunsen burner. The rem- 
edy is to turn off the gas, decrease the air supply and 
relight. With poor gas pressure there is sometimes no 
remedy except to allow the pipes to cool. 

6. The Oxyhydrogen Blowpipe. — This burner has been 
described elsewhere, under hydrogen. If the flame ob- 
tained by this torch or with acetylene be examined, it 
will be seen to consist of only two portions — a very 
small inner cone and a nearly invisible outer one. The 
gases used are so proportioned and so thoroughly mixed 
before they issue from the tip that the combustion is 
perfect throughout nearly the entire mass. Further, it 
will be seen that the flame is relatively a small one. The 
result is a flame of very great intensity. 

7. The Blast Lamp. — The construction of the blast 
lamp is not essentially different from that of the oxy- 
hydrogen torch. The inner pipe is attached either to a 
foot bellows or to a tank of compressed air, while the 
outer connects with the gas supply. Before the air is 
turned on, the gas burns with a large, flickering, yellow 
flame, with low temperature. With the air, the flame 
decreases greatly in size, loses its yellow portion, be- 
comes blue and almost invisible, and has a high tern- 



196 APPLIED CHEMISTRY 

perature. The admixture of the air in the tube enables 
the entire amount of the gas to be consumed within a 
small space, so that the heat is all concentrated therein. 

Exercises for Review 

1. What is a flame? Show that what you say is true of the can- 
dle and of a kerosene lamp. 

2. Give some experimental proof that a stream of gas is being 
formed in the candle wick. 

3. What is the explanation of the flame above a hard coal fire? 

4. Explain combustion in a broad sense. Show how air may be 
"burned." 

5. Of how many portions does an ordinary flame consist? 

6. Give some simple experiments to show something as to the 
character of the innermost part of a flame. 

7. What does the middle cone contain? What proof can you 
give ? 

8. What is the character of the outer cone? How do you think 
it would appear different at night from in the daytime? 

9. What is meant by incandescence? 

10. Describe the Bunsen burner as found on your desk. 

11. What effect does the construction of the Bunsen burner have 
on the structure and character of the flame ? 

12. Why is the flame shorter when the air is on at the bottom? 

13. Explain why a burner strikes back and give the remedy. 

14. What applications of the Bunsen burner are found in most 
city homes? 

15. What is the trouble when a gas flame on a cook stove burns 
yellow? How can it be remedied? 

16. Explain why the oxyhydrogen flame is so intense in heat. 

17. Describe the construction of the blast lamp. Why is the 
flame so large before the air is turned on? 



CHAPTER XVI 

METHODS OF LIGHTING 
Outline — 

Primitive Methods of Lighting 
Kerosene Lamps 
Gas Illumination 
Incandescent Electric Lights 
The Welsbach System 
Tungsten Electric Lamps 
The Lime Light 
Arc Lights 

1. Primitive Methods of Lighting. — When man first 
began to use artificial light is not known. Probably in 
some localities, at first it was the pine knot full of resin; 
in others, a bowl of oil into which was clipped a twisted 
rag or something which served as a wick. Miners, even 
now, often carry upon their caps a lamp containing a 
thick oil with a wick enclosed in a tube. Such lights 
are necessarily poor, more or less unsteady, and produc- 
tive of smoke. The candle was an improvement upon 
the old, open oil lamp. At first, tallow was used and 
later the oil of the sperm whale. Sometimes, even now, 
for hard candles, tallow is treated with an acid to pre- 
cipitate the stearic acid from the stearin and this is 
melted and molded into shape. Those most commonly 
used, however, are made of paraffin, obtained from pe- 
troleum. The light obtained is due, as explained in a 
preceding chapter, to the presence of the incandescent 
carbon particles in the flame. 

2. The Kerosene Lamp. — A decided advancement was 
made in lighting when the kerosene lamp was invented. 
The principle is not different from thai of the candle. 

m 



198 



APPLIED CHEMISTRY 



By capillarity the oil is drawn up through the wick 
and burned at the top. The chimney is the source of 
the increased light. By means of the perforations in 
the support for the chimney at the bottom a draft is se- 
cured so that the combustion is more rapid, the carbon 
particles in the incandescent zone reach a higher tem- 
perature and, therefore, give more light. Moreover, the 
flame is a steady one and produces less smoke. In ear- 
lier years there was frequently more or less gasoline 




Fig. 45. — Determination of flash point of an oil. 



mixed with the kerosene, for at that time there was no 
demand for the lighter oil. As a result, explosions 
were not uncommon. This led to legislation requiring 
all merchantable kerosene to be insj^ected and possess 
a certain " flash point." This means the temperature 
at which the vapor arising from it will ignite. It may 
be shown fairly well by a very simple method, as seen 
in Fig. 45. A thermometer is supported on a stand at 
such a height as to dip within some gasoline or kerosene 
in a beaker. A piece of cardboard with an opening 



METHODS OF LIGHTING 199 

cut on one side covers the beaker. The oil is then slowly 
and cautiously heated with a small flame. At intervals, 
a small wax taper, lighted, is brought to the opening in 
the cardboard. The temperature at which the vapor 
arising catches fire or "flashes" through the space above 
the oil is called the flash point. At the present time, 
since gasoline is the valuable product obtained from pe- 
troleum, kerosene is always free from the more volatile 
oil and explosions are almost unknown. 

3. Gas Illumination. — The next step in artificial light- 
ing was by means of gas, at first made from soft coal. 
For its combustion a burner was used closed at the top 
by a little cap made of fire clay or some similar non- 
combustible material, with a narrow slit for the escape 
of the gas. When ignited a thin, fan-shaped flame was 
the result. The light produced was the result of the 
incandescent carbon particles as in other cases already 
studied. 

4. Electric Lights. — The next improvement in light- 
ing systems was that of the incandescent electric bulb. 
It had long been known that a wire of high resistance 
carrying an electric current would become luminous. 
Attempts Avere made with platinum and other metals in 
electric lamps, but none of them gave sufficient light to 
be of value. Finally, after years of experimenting with 
all sorts of vegetable fibers, one from a special bamboo 
was obtained sufficiently strong to be used in a lamp. 
Later, these carbon filaments were obtained by carbon- 
izing threads made from a viscous solution of cellulose, 
much as fiber silk is now. The air was pumped out of 
the bulb, so as to prevent the rapid disintegration or 
combustion of the carbon thread. Tn such lamps, it 
will be seen that the light, as in all other cases already 
mentioned, is obtained by incandescent carbon. Natu- 



200 APPLIED CHEMISTRY 

rally, they were called incandescent lights. The con- 
venience of turning on or off such lamps was great, and 
the candle power was higher, but the quality of the 
light otherwise was not essentially different from the 
gas-light. 

5. The Welsbach Mantle. — Two things led to the in- 
vention of the gas mantle. One was the discovery of 
natural gas, and the desire to use it for illuminating 
purposes. As it is low in carbon content, when burned 
in the old-fashioned slit-top burner, it gives very little 
light, not sufficient to be of value. The other reason 
was the greater convenience offered by electricity with 
the resulting strong competition, threatening to dis- 
place gas entirely. At such a time the mantle was in- 
vented by a man named Welsbach. It is made by spray- 
ing upon a little hood made from long fiber mercerized 
cotton, a mixture of thorium and cerium nitrates, 99 
parts to 1. The burner upon which it is used is almost 
identically that invented by Bunsen. For use the man- 
tle is hung over the burner and ignited. The cotton 
burns off, while the two nitrates by the heat are con- 
verted into oxides. Now, when the gas is ignited, the 
burner gives a short, hot flame which heats the two ox- 
ides into incandescence just as the oxyhydrogen flame 
does the stick of lime, which is calcium oxide. At the 
temperature obtained, the oxides give a beautiful, white 
light, six or eight times as strong as the old style tip. 
Natural gas can be used in this burner as well as arti- 
ficial. The quality of the light is greatly superior to 
that of the incandescent carbon electric, and not essen- 
tially different in candle power. 

6. Acetylene. — This gas has been mentioned elsewhere 
although it is used more for illumination than for cook- 
ing purposes. It must be burned in a special tip and 
cannot be used w r ith the Welsbach mantle. It gives a 



METHODS OF LIGHTING 201 

beautiful white light, but as the gas must be manufac- 
tured in the place where it is be used, it is not adapted 
to the wants of a city. Its field must always be the 
suburban or country home. 

7. The Tungsten Lamp. — The quality of the light af- 
forded by the Welsbach gas system stimulated the elec- 
tric companies to discover some filament which would 
give a white light comparable with gas. Several sub- 
stances other than carbon have been tried, but at the 
present time tungsten is regarded as the most desira- 
ble. When first adopted such lamps were very fragile, 
owing to the brittleness of the filament, and gained 
slowly in favor. They have been perfected now, how- 
ever, so that they are practically as durable as the car- 
bon filaments. They give a brilliant white light, and 
consume much less current for the same candle power 
than the old style lamp. An improved form of the 
tungsten lamp now has the bulb filled with nitrogen 
instead of the usual vacuum. They are more durable 
and at the same time give a better light. Without acci- 
dent a tungsten lamp should give about 1,000 hours of 
actual service. 

8. The Calcium or Lime Light. — This has been men- 
tioned elsewhere as the Drummond light. The principle 
is not different from that seen in all other cases and is 
due to the incandescence of a solid. In this case it is 
the stick of lime, calcium oxide, upon which an intensely 
hot flame is allowed to strike. Its brilliance rivals that 
of the electric arc. Its use has been mentioned else- 
where. 

9. Arc Lights. — In arc lights two sticks of gas carbon 
are used which in service are separated from each other 
by a short distance. An electric current of high voltage, 
in spanning the gap, does so not in a straight line, but 
curved like the arc of a circle. The positive carbon 



202 APPLIED CHEMISTRY 

is worn away and the particles, white hot, are carried 
across the gap and in part deposited npon the negative 
carbon. It is these white-hot particles which produce the 
dazzling light. At first the two carbons were used in large 
globes entirely exposed to the air. As a result they 
were burned away rapidly, so that a great deal of time 
was needed in replacing them, in addition to the ex- 
pense of the carbons themselves. At the present time 
they are enclosed in small globes. These are not air- 
tight, but through combustion they are soon filled with 
carbon dioxide so that the subsequent disintegration is 
slow. Arc lights are used mainly for lighting of streets, 
and spot lights for stage effects. 

Exercises for Review 

1. Name some of the different kinds of candles made. How is 
light produced in a candle? 

2. Explain why the kerosene lamp gives better light than the 
candle. Why were they explosive at first? 

3. What is meant by the flash point of an oil? How may it be 
obtained approximately ? 

4. Describe the tip used in the original gas lamp. What pro- 
duces the light in such a flame? 

5. Describe the incandescent carbon lamp. How are the car- 
bon filaments made now? How originally obtained? 

6. What objection to the carbon electric? What advantage has 
it over gas? 

7. Describe the Welsbach mantle and burner. What are its ad- 
vantages? 

8. What kind of a tip is used with acetylene? Where are acety- 
lene lights seen frequently? To what kind of lighting is it essen- 
tially suited? 

9. How is the tungsten lamp different from the old carbon? 
What objection was there to them at first? 

10. In working about a tungsten lamp, as in dusting or cleaning, 
what can be done to render them still less liable to break? 

11. How is the calcium light obtained? For what is it used? 

12. Why are arc lights so named? Where used? What produces 
the light? Where are the carbons obtained whi'di are used in the 
arc light? 



CHAPTER XVII 

SOME ORGANIC COMPOUNDS 
Outline — 

Hydrocarbons 

(a) Methane 

(6) Gasoline and Kerosene 

(c) Derivatives of Methane 
The Alcohols 

(a) Wood Alcohol 

(b) Grain Alcohol 
Organic Acids 

(a) Formic 

(b) Acetic 
Aldehydes 

Formalin 
Ethers 

1. Hydrocarbons. — It lias been stated elsewhere that 
the study of carbon compounds constitutes a separate 
branch of chemistry, known as "Organic Chemistry." 
The compounds were originally so named because, as 
far as observed, they were produced only by. organized 
life forces. This is known now not to be true. From 
their very great practical value in everyday life with 
some of these compounds it is important that the student 
should become familiarized. Among the simplest of 
such compounds are the liydrocar'bons, which contain as 
the name indicates only carbon and hj^drogen. In a pre- 
ceding chapter marsh gas has been mentioned, as have 
also gasoline, kerosene and various other oils derived from 
petroleum. All these are really paraffins and belong to 

203 



204 APPLIED CHEMISTRY 

a regular series in which over sixty have been prepared. 
The first six are here given, 

Methane, CH 4 , 
Ethane, C 2 H 6 , 
Propane, C 3 H 8 , 
Butane, C 4 H 10 , 
Pentane, C 5 H 12 , 
Hexane, C 6 H 14 . 

The subsequent members of the series receive their names 
from the Greek numerals as the last two given above, the 
first part of the name indicating the number of carbon 
atoms. Examination of the formulas shows that the dif- 
ference between any two successive members is CH 2 ; 
hence, it becomes a simple matter to write formulas for 
the entire series. Further it will be observed that the 
hydrogen is always twice the carbon plus two. The gen- 
eral formula for any paraffin, therefore, is C n H 2n + 2 in 
which n rejDresents the number of the carbon atoms. Of 
the more than sixty paraffins known, the first five are 
gases, then follow a very considerable number of liquids, 
and above these are the solids with which all are familiar 
in the white wax of commerce. 

2. Methane. — This is commonly known as marsh gas, 
because of the fact that it is produced in swamps and 
stagnant creek beds where decomposition of leaves and 
other organic matter is taking place. It occurs in coal 
mines, and is known by the miners as fire damp, the 
word damp being their name for gas. It is so called be- 
cause of its dangerous, explosive character. It is this 
gas which causes practicallly all the explosions in coal 
mines. As in such cases the combustion is more or less 
imperfect from the limited supply of air, much carbon 
monoxide usually exists in the mine following the explo- 



SOME ORGANIC COMPOUNDS 205 

sion. This lias been mentioned before as the fatal black 
damp. It has been mentioned, also, that methane is the 
chief constituent of natural gas, is more than 40 per cent 
of coal gas, as well as a very considerable part of water 
gas. It is colorless, has a density only eight times that 
of hydrogen or little more than half that of the air, is 
odorless, and burns with an almost invisible blue flame. 
On account of its having no odor its presence in mines 
cannot be detected by the senses. For protection against 
it, more than a century ago, Sir Humphrey Davy in- 
vented a safety lamp which consists really of very little 
more than a chimney of fine wire gauze, surrounding the 
flame, like the chimney on a lantern. All it does is to 
prevent the gas on the outside from becoming heated 
to its kindling temperature. This will be understood if 
a wire gauze be held above a burning Bunsen flame. Ap- 
parently, it is possible by means of the gauze to push the 
flame down. Really, however, what it does is to conduct 
the heat away from the gas and dissipate it so that the 
gas in passing through is cooled below its kindling point. 
That this is so may be shown by bringing a flame to the 
current of the gas above the gauze. It is quickly ignited 
and goes on burning. 

3. Gasoline and Kerosene. — Gasoline consists mainly 
of the sixth, seventh and eighth of the paraffin series, 
hence is a mixture. Benzine and the other light oils 
mentioned as belonging to the gasoline fraction obtained 
from petroleum below 150° C. may be separated from 
each other by taking smaller fractions. To illustrate, 
a sample of gasoline may begin to boil at about 75° C: 
the petroleum ether comes off first and because it has a 
very low boiling point it is soon all distilled over. The 
receiving flask will then be removed and another at- 
tached for 1ln> next fraction. Kerosene consists of the 



206 APPLIED CHEMISTRY 

eight paraffins just above the gasoline series. Having 
seen the close relation of the various oils to each other 
in the paraffin series, it is less difficult to understand 
how by "cracking" it might be possible to convert the 
higher members into the lover, since a single molecule 
of the heavy oils might make two or more of the lighter 
ones. 

4. Derivatives of Methane. — A derivative as the term 
is used here is a compound obtained by substituting 
an atom or atoms of some element or some radical group 
for one or more of the hydrogen atoms in the com- 
pound. One of the most simple as well as familiar de- 
rivatives of methane is chloroform, CHCL, obtained in- 
directly by substituting three atoms of chlorine for 
three of the hydrogen in methane. Iodoform, men- 
tioned elsewhere, is a corresponding derivative with 
the formula, CHI 3 . Carbon tetrachloride, mentioned as 
a good fire extinguisher, is also a derivative in which all 
the hydrogen in methane has been replaced by chlorine. 
Chloroform is a colorless, oily liquid of rather pleasant 
odor and not inflammable. Its use as an anesthetic is 
familiar. It has the advantage over ether that it may 
be used near an open flame without danger. 

5. The Alcohols. — There are two, familiar to all, 
methyl, or wood alcohol, and ethyl or grain alcohol. They 
are derivatives of the first two paraffins : thus, CH 4 — > 
CH 3 OH, and C 2 H 6 -» C 2 H 5 OH, in both of which a hy- 
droxy! group has been substituted for a hydrogen atom. 
Each of the paraffins has a corresponding alcohol, the 
higher ones in the series being white crystalline solids. 
Wood alcohol is obtained by the destructive distillation 
of wood in making charcoal. It is a colorless liquid, if 
pure, has a somewhat unpleasant odor, is very poison- 
ous, inflammable and an excellent solvent for many 



SOME ORGANIC COMPOUNDS 207 

tilings. Because of this last property it has many uses 
as in making shellac, and similar preparations. How- 
ever, denatured alcohol, being much cheaper, is fast tak- 
ing the place of the wood alcohol in many cases. It is 
grain alcohol, adulterated by the addition of about 10 
per cent of methyl or wood alcohol or some other liquid 
to render it more or less disagreeable in odor, and unfit 
for medicines, extracts or as a beverage. Adulterated, as 
mentioned, it is often called methylated spirits. The United 
States government has specified at least eight formu- 
las for denaturing alcohol to meet the various demands 
of manufacturers. It now has very extensive uses. It 
is one of the most commonly employed substances to 
prevent the freezing of the water in radiators of motor 
cars and trucks. Ethyl alcohol is made from grains. 
These are kept damp and warm for several days till 
sprouted. During this time a ferment called diastase, 
present in the seed and provided by nature to convert 
the insoluble starch present into soluble form, so that the 
embryo plant and rootlets can use it, has changed the 
starch into a form of sugar. At the proper stage, learned 
by experience, the grain is heated to stop the process ; it 
is then ground, yeast is added and fermentation begins 
whereby the sugar into which the starch was converted 
changes into alcohol and carbon dioxide. Thus, 

C 6 H 12 6 -» 2C 2 H 5 OH + 2C0 2 . 

When the fermentation is completed the alcohol is dis- 
tilled out and put upon the market about 95 per cent 
strength. If absolute alcohol is desired it may be ob- 
tained by treating the commercial variety with lime or 
anhydrous copper sulphate and distilling carefully. 
Grain alcohol is a colorless liquid, of pleasant odor, boil- 



208 APPLIED CHEMISTRY 

ing point of 78° C, and almost as poisonous as methyl . 
It is nsed in preparing many medicines as a solvent or 
preservative, in extracts for domestic or other purposes, 
and in a great variety of other ways. 

6. Organic Acids. — From each of the alcohols, by oxi- 
dation, an acid may be derived. Tims, if two of the hy- 
drogens in an alcohol are removed and an oxygen atom 
substituted for them, an acid is obtained. Methyl al- 
cohol thus gives formic acid, HCOOH. The equations 
for the first two are 

CH 3 OH + 2 -* HCOOH + H 2 0, 
C 2 H 5 OH + 2 -> CH 3 COOH + H 2 0. 

Like the paraffins and the alcohols, the acids differ by 
CH 2 , so that the entire series is easily written. These 
two acids might be given thus, H 2 C0 2 and H 4 C 2 2 ; but 
they are usually presented, as above, to indicate the 
structure of the molecule, and this is decidedly pref- 
erable. The empirical formula, H 4 C 2 2 , tells nothing 
but the number of atomic weights of each element pres- 
ent, from which may be calculated the percentage com- 
position : the graphic formula indicates that three hy- 
drogen atoms are attached to one carbon atom, and 
that the two oxygen atoms are attached to the other 
carbon but not in the same manner, and that the remain- 
ing hydrogen atom is attached to the second oxygen. 
It is more fully shown thus, 

H 

H-C-C-O-H. 

I 
H 

The first acid has little commercial value. It is secreted 
bv some ants and received its name from the Latin word 



SOME ORGANIC COMPOUNDS 209 

for ant, forma. It is also secreted by the stinger gland 
of snch insects as the wasp, bee, and the hornet, when ex- 
cited. The pure acid is a colorless liquid, and upon the 
skin causes intense pain and produces blisters. It is this 
acid injected hypodermically, that causes the pain when 
stung by any of the above insects. Acetic acid is widely 
used in a diluted form, 2 to 5 per cent, as vinegar. Orig- 
inally, it was obtained largely from apple cider through, 
first alcoholic fermentation, when the cider became hard, 
and then subsequent oxidation by means of another spe- 
cies of bacterium. At the present time the demands are 
too great to be met in this way. Some is obtained in the 
distillation of wood in making charcoal ; some in the fer- 
mentation of fruit juices other than that of the apple; 
but most comes from the glucose prepared from corn 
starch. A solution of the glucose is passed slowly through 
tanks or barrels filled with shavings, previously inoculated 
with the bacterium, Mycoderma aceti, familiarly known 
as "mother of vinegar." The process is rapid and the 
vinegar obtained is free from the many organic impuri- 
ties of the old-time product, especially the decayed pulp 
of the apple. It also does not contain the vinegar eel, a 
tiny white worm, which frequently may be seen in count- 
less numbers in cider vinegar if examined carefully. 
Pure acetic acid is a colorless liquid, which becomes solid 
at 16.7° C. It is often called glacial acetic for this reason. 
7. Aldehydes. — From each alcohol in the series a cor- 
responding aldehyde may be obtained. This is done by 
carrying the oxidation only far enough to remove two 
atoms of hydrogen without introducing anything in 
their place. This leaves them unsaturated compounds ; 
hence, they are reducing agents. The only one of im- 
portance is formaldehyde, which is prepared from methyl 



210 APPLIED CHEMISTRY 

alcohol. All the aldehydes obtain their names from the 
corresponding acid, hence, the name in this case. The 
preparation from methyl alcohol is shown by the equa- 
tion, 

2CH 3 OH + 2 -^ 2HCOH + 2H 2 0. 

Formic aldehyde is a gas which liquefies at -21° C. For 
use it is dissolved in water and is put on the market 
under the name of formalin, a 40 per cent solution. From 
this the gas is constantly escaping, irritating in odor, 
affecting both the nostrils and eyes. It is strongly germi- 
cidal and is used extensively for disinfecting purposes. 
This is easily done by pouring the solution upon lime 
with which the water present reacts giving sufficient heat 
to expel the gas rapidly. Since it is a hardener of tis- 
sues and cheaper than alcohol it is used extensively in 
preserving various zoological and botanical specimens. 

8. The Ethers. — Corresponding to each alcohol is an 
ether. From ethyl alcohol is obtained the only impor- 
tant one, ethyl ether. Its formula is (C 2 H 5 ) 2 0, which 
indicates that it is an oxide of the ethyl group. It is 
a colorless liquid, of sweet pleasant odor, with a boiling 
point below the temperature of the human body, 34.9° 
C. It is very inflammable, and an excellent solvent of 
iodine, as also of oils and fats. Inhaled it produces 
anesthesia. It is regarded as a safer anesthetic than 
chloroform, but cannot be used near an open flame. 

Exercises for Review 

1. What is a hydrocarbon? Name six with formulas. What is 
an organic compound? What is a paraffin? 

2. How many paraffins are known? What is their physical con- 
dition? 

3. Give two other names for methane. How does it receive these? 



SOME ORGANIC COMPOUNDS 211 

4. Describe the safety lamp and explain how it works. 

5. Of what does gasoline consist? Into what several oils may 
it be separated? What is this process called? 

G. Name two halogen derivatives of methane and use of each. 

7. Name two alcohols with formulas. To what class of com- 
pounds do they belong? 

8. What is denatured alcohol? Give some uses for it. 

9. What is methylated spirits? What is a ferment? 

10. How is grain alcohol made? Give uses. 

11. Name two important organic acids. From what are they 
derived ? 

12. Where does each of these occur in Nature? 

13. How is the commercial supply of vinegar obtained? 

14. What is the common aldehyde? Its trade name? Uses 
for it? 

15. Give formula for common ether. Of what use is it? Com- 
pare with chloroform. 



CHAPTER XVIII 

ETHEREAL SALTS, OILS, FATS. SUGARS 

Outline — 

Esters or Ethereal Salts 

Glycerol 

Esters of Glycerine 

Oleomargarine 

Compound Lards 

Molecular Structure of Fats 

The Olefins 

Hydrogenation of Oils 

The Carbohydrates 

(«) Monosaccharides 

(&) Disaccharides 

(c) Polysaccharides 

1. Esters. — It will be remembered that a base is a hy- 
droxide. By examining the formulas of the alcohols it- 
will be seen that they are hydroxides. They are organic 
bases and. combined with organic acids, they produce 
what are called ethereal salts or esters. The first term 
is used for the reason that many of them have pleasant 
odors somewhat resembling ether. The word, ester, is 
coined from the other two and has no meaning. Several 
of these ethereal salts are familiar in the form of arti- 
ficial flavors and extracts, such as banana, pineapple, and 
the like. They may be had of the grocers and are found 
at soda fountains in some of the syrups used. Thus, 
artificial pineapple is ethyl butyrate, an ester of grain 
alcohol and butyric acid. It is the latter that gives the 
strong, disagreeable taste to rancid butter: apple is amy! 
valerate, and pear, isoamyl acetate. The ester formed by 
the union of ethyl alcohol and acetic acid has a pleasant 

212 



ETHEREAL SALTS, OILS, FATS, SUGARS 213 

fruity odor and is easily made in the laboratory. It is 
sometimes used as a test for the presence of alcohol in a 
substance. 

2. GlyceroL — This compound is commonly known as 
glycerine. Its formula, C 3 H 5 (OH) 3 , shows that it is an 
organic base with three hydroxyl groups; it is, there- 
fore, an alcohol. It is obtained as a by-product of the 
soap industry. In home-made soaps it is not separated 
out and in some special varieties of factory-made, such 
as the transparent soaps. But the great demand for 
glycerine in the manufacture of explosives as described 
elsewhere and the fact that it adds little to the value 
of the soap for general purposes, has led to its careful 
separation. Glycerine is a sweet syrupy liquid, nearly 
colorless if pure and very soluble in water. It derives 
its name from the Greek word for sweet on account of 
its taste. Because of the fact that it is hygroscopic, when 
the price will permit, it is sometimes used in small quan- 
tities by bakers in cakes to prevent their drying out so 
rapidly. It is also used in toilet and other pharmaceuti- 
cal preparations, but the greater proportion goes to the 
explosive factories. 

3. Esters of Glycerine. — It is the salts of glycerine 
that chiefly interest us, for they are the common fats 
and oils used as foods. The four most common are 

Glyceryl butyrate, Butyrin, C 3 H 5 (C 3 H 7 COO) 3 , 
Glyceryl palmitate, Palmitin, C 3 H 5 (C 15 H 31 COO) 3 , 
Glyceryl oleate, Olein, C 3 H 5 (C 17 H 33 COO) 3 , 
Glyceryl stearate, Stearin, C 3 H 5 (C 17 H 35 COO) 3 . 

All the common fats and oils are mixtures of three or all 
four of these. Butter contains all four; when free from 
water the butyrin is about 8 per cent of the whole. It 
is this ester that gives the characteristic pleasant odor 



214 APPLIED CHEMISTRY 

and taste to butter. Ordinarily, there is in butter about 
12 to 14 per cent of water, with some casein from the 
milk. Olive oil is about 75 per cent olein. Of the four 
fats mentioned, olein has the lowest melting point, being 
a liquid at ordinary temperatures, and stearin has the 
highest. Any fat. therefore, with a high proportion of 
olein will melt easily and may be liquid at all ordinary 
temperatures; thus, cotton-seed oil and "niazola," an oil 
made from corn as a by-product in the manufacture of 
starch and glucose, are high in olein. Common lard is 
about 60 per cent olein and melts easily, while beef fat is 
high in stearin. It will be seen, therefore, that the vari- 
ous edible fats, whether from beef. pork, mutton, or of 
vegetable origin, are very similar in character. If the 
formulas given above are examined, this fact is even 
greatly emphasized. 

4. Oleomargarine. — The demand for butter is far 
greater than the supply. This has led to the preparation 
of artificial butters, most of which are called oleomar- 
garines. These are made by the mixture of animal and 
vegetable oils, which are much cheaper than butter. One 
formula, used by one of the large packing houses, is 
given below. 

Neutral lard. 75 pounds 
Cottonseed oil, 175 pounds 
Oleo oil. 675 pounds 
Peanut oil. 75 pounds 

These are put into 60 gallons of milk from which the 
cream has been separated and churned. The purpose 
of this is to add something of the flavor of real butter 
and possibly some of the casein of the milk. The fats 
are removed from the milk, and 150 pounds of real but- 
ter and 125 pounds of salt are added and the whole 



ETHEREAL SALTS, OILS, FATS, SUGARS 215 

thoroughly worked together. This gives a total weight 
of solids of 1,275 pounds. In the churning and subse- 
quent working of the mixture considerable water, even 
as much as 12 per cent is taken up, so that there is 
finally a total weight of between 1,400 and 1,500 pounds. 
In this variety it will be seen the butter is approximately 
10 per cent of the whole. In another formula used, 
the real butter mixed with the other fats may run as 
high as 25 per cent, but it is understood that this par- 
ticular brand is not put on the general market but sold 
entirely to special customers. Many brands contain no 
butter at all. At the present time oleos in which cocoa- 
nut oil enters to a very considerable extent are being 
manufactured by nearly all the large packing compa- 
nies. The advantage claimed for these butters is that co- 
coanut oil contains about 5 per cent of butyrin ; hence, 
they much more nearly approach real butter in com- 
position and taste than do those with a higher percent- 
age of animal oils. For years after their introduction 
into the United States there was great objection made 
to them by the butter producers and much adverse legis- 
lation resulted. They may not be colored, although all 
creamery butter and cheese are ; moreover, oleos, must 
pay an excise tax, which somewhat increases their cost to 
the general public. Nevertheless, these artificial but- 
ters are clean, wholesome articles of food, nutritious, and 
to all purposes, of practically the same food value as 
the real article. There is only one objection and that 
is the low melting point ; thus in warm weather oleo- 
margarine is more difficult to keep as hard as is desira- 
ble. In spite of adverse legislation and the prejudice 
existing, their consumption has increased wonderfully 
in the last five years. Some idea of this may be obtained 
from the government reports concerning the import a- 



216 APPLIED CHEMISTRY 

tion of cocoanut and other vegetable oils. The follow- 
ing table gives the amounts for the years 1914 and 1918, 
the last available at this time. 



Oil 1914 


1918 


Peanut Oil 
Soy Bean Oil 

Cocoanut Oil 


1,000,000 gals. 
16,000,000 lbs. 
74,000,000 " 


Over 8,000,000 gals. 
337,000,000 lbs. 
259,000,000 " 



5. Artificial Lards. — As the high price of butter and 
the inadequate supplies have led to the substitution of 
oleos, so has it been in the case of lard. The demand 
is vastly greater than the supply and today a consider- 
able number of so-called "compound lards" are found 
on the market. Such are "Suetene," "Cottolene," 
"White Cloud," "Snowdrift," and numbers of others. 
As the names of some indicate, many of them contain 
more or less of cotton-seed oil. But as this runs high 
in olein it is liquid at ordinary temperatures. The 
public is accustomed, however, to a solid fat for short- 
ening and for various other food purposes; hence, it 
is slow to accept a liquid, however equally good it 
might be. Efforts were made, therefore, to overcome 
this difficulty, and these have been eminently successful 
as will be shown later in this chapter. 

6. Structural Composition of Fats. — With the excep- 
tion of olein the fats mentioned in this chapter may be 
regarded as derivatives of the paraffins. Thus, butane, 
C 4 H 10 , is the fourth in the paraffin series. The acid de- 
rived from it, butyric, would have the formula, 
C 3 H 7 COOH. Combining this acid with the base, glyce- 
rol, as shown by the equation, 

C 3 H 5 (HO) 3 + 3C 3 H 7 COOH -> 3H 2 + C 3 H 5 (C 3 H 7 COO) 8 
we have butyrin. As the paraffins are all saturated com- 
pounds, so are the glyceryl salts derived from them. To 



ETHEREAL SALTS, OILS, FATS, SUGARS 217 

illustrate: Methane, ethane and butane are respectively 
represented by the structural formulas, 

H H H HH HH 

I II I I I I 

H-C-H H-C-C-H H-C-C-C-C-H, and butyric 

I II I I I I 

H H H HH HH 

HH HO 

acid by H-C-C-C-C-O-H. 

I I I 
HH H 

In all these it is seen that every carbon atom is fully 
saturated; so are the esters as may be seen in the fol- 
lowing formula for butyrin. To the glyceryl radical, 
(C 3 H 5 ) three carbon chains are attached, but only one 
is written for the sake of convenience, 

HH HO 

I I I I 
H_C-C-C-C-0-(C,H, ( ) =. 
I I I 
HH H 

7. The Olefins. — There is another class of hydrocar- 
bons to which attention must be directed in order that 
the preparation of compound lards may be understood. 
These are the olefins, many in number, of which the 
first few of the series are given. 

Ethylene, C 2 H 4 , 

Propylene, C 3 H 6 , 

Butylene, C 4 H 8 , 

Amylene, C 5 H 10 , also called Pentylene, 

Hexylene, C 6 H 12 . 

It will be observed that they are given names derived 
from those of the paraffins, with the ending changed. 
There is no olefin corresponding to methane. These com- 
pounds may also form acids and alcohols as in the case 



218 APPLIED CHEMISTRY 

of the paraffins. The important distinction to be noticed 
at this time is that these are unsaturated compounds. 
A proof of this was given in the case of ethylene on p. 

HH 

I I 
180. Structurally, this would be represented thus, -C-C-, 

I I 
HH 

which shows two of the carbon atoms with one free bond. 
In the same way the acids and the esters derived from 
them would be unsaturated. Therefore, olein, belonging 
in this group, is an unsaturated compound. If the for- 
mulas for stearin and olein be compared, it will be ob- 
served that they differ only by two atoms of hydrogen, 
yet one is a hard white solid, and the other a liquid at 
ordinary temperatures. Without attempting to write the 
entire carbon chain, they may be compared thus, 

HHHO 

Chain of Carbon-C-C-C-C-0-(C 3 H 5 ) =2 Carbon Chains, 

I I I 
HHH 

H HO 

II Mi 

Chain of Carbon-C-C-C-C-0-(C 3 H 5 ) =2 Carbon Chains. 
I I I 
H H 

The first of these is stearin, the second, olein. 

8. Hydrogenation of Oils.— If the above statements 
are true it would seem that if it were possible to cause 
the unsaturated carbon atom in olein to take up two 
additional atoms of hydrogen, the olein should be 
changed into stearin with a corresponding change in 
melting point. This has been found possible and the 
process is called hydrogenation. A current of hydrogen 
introduced into any of these oils has no effect, but if a 



ETHEREAL SALTS, OILS, FATS, SUGARS 219 

catalytic agent be used, more often nickel in this case, 
the unsaturated olein takes up the additional hydrogen 
and at room temperature becomes a white solid. The 
process has the greatest commercial value. "Crisco, " as 
well as the various compound lards mentioned, are vegeta- 
ble oils, thus hydrogenated, or they are mixtures of the 
same with animal fats. Wesson oil is cotton-seed oil pre- 
pared by a certain process for cooking purposes. All the 
edible vegetable oils such as those made from corn, pea- 
nuts, cotton seed, soy beans, cocoanuts, are now being 
hydrogenated and made into pure white solid fats. They 
are all wholesome, probably even more so than those of 
animal origin, because not subject to disease and equally 
valuable as energy and heat producers. 

9. The Carbohydrates. — The organic compounds con- 
sidered thus far in this chapter have all been hydrocar- 
bons and derivatives from them. There is another very 
important class known as the carbohydrates, which as 
the name indicates contain carbon, hydrogen and oxygen. 
The hydrogen and oxygen with scarcely any exception 
are in the proportion of 2 to 1. Three of the most com- 
mon, which are typical of the three classes are 

Glucose, C 6 H 12 6 , a monosaccharide, 
Cane Sugar, C 12 H 22 1]L , a disaccharide, 
Starch, (C 6 H 10 O 5 )n, a polysaccharide. 

The prefixes mono-, di- and poly- refer to the number of 
aldehyde or ketone groups which the various compounds 
in these three classes contain. One aldehyde, HCOH, has 
been studied, but the ketones are not of sufficient im- 
portance to demand our attention here. The group -COH 
is contained in all aldehydes; glucose has one of these 
groups, cane sugar two, and starch several or many. Glu- 
cose is one of several sugars with the same empirical for- 



220 APPLIED CHEMISTRY 

mula, found in nature in various fruits. It is manufac- 
tured extensively from corn starch. The oil is first re- 
moved from the corn; in water under the action of di- 
lute sulphuric acid, the starch takes up two additional 
atoms of hydrogen and one of oxygen for each saccharide 
group, thus, 

C 6 H 10 O 5 + H 2 O^C 6 H 12 O 6 . 

The sulphuric acid used is merely catalytic and is re- 
moved by adding lime or some similar substance which 
converts it into an insoluble compound, so that it settles 
out. The glucose is then concentrated and put on the mar- 
ket mostly in the form of a syrup under a variety of 
trade names. One of the most advertised is "Karo," 
which may be had in a dark variety, the natural color, 
and a light variety, which has been bleached by sulphur 
dioxide. Glucose, while only about three-fifths as sweet 
as cane sugar, is a wholesome article of food notwith- 
standing a popular prejudice against it. This has come 
through a misunderstanding regarding the sulphuric acid 
used in the inversion of the starch. The bleached or color- 
less syrups may sometimes contain a trace of the gas used 
in the process of bleaching, but this objection cannot be 
offered to the dark syrups. Much of the candy on the 
market contains more or less glucose. Probably the only 
objection that can be offered is that it absorbs moisture 
from the air more readily than that made from cane 
sugar, and thus in damp weather tends to become 
"sticky." Glucose, as a food, is more readily assimilated 
than cane sugar ; in fact, the latter, before assimilation, 
must be changed by the digestive fluids into the monosac- 
charide variety. 

10. The Disaccharides. — Cane and beet sugar are the 
two most abundant of this class and have the same com- 
position. Their source is well known and need not be 



ETHEREAL SALTS, OILS, PATS, SUGARS 221 

discussed here. Milk sugar, obtained as a by-product 
from the whey in cheese factories, differs from the two 
already mentioned in that it contains a molecule of com- 
bined water, thus, C 12 H 22 11 .H 2 0. Milk becomes sour 
through the changing of this sugar into lactic acid just 
as acetic acid is produced in cider through the fermen- 
tation of the fruit sugar contained in the apple. The 
lactic acid produced thus converts the casein, originally 
present in the soluble form, into the insoluble variety, 




Fig. 46. — Starch granules. The shape of the granules is different in the 
various starch-containing foods, so that under the microscope the variety 
may be readily recognized. 

so that the milk becomes "curdled." The same thing 
occurs in the stomach through the action upon the casein 
of the hydrochloric acid always normally present. 

11. Starches. — A large number of plants produce 
starch. The most familiar to us are the grains, such 
as wheat and corn, and the potato. All have the same 
formula, but under the microscope, their granules are 
very different in shape (Fig. 46). The number of sac- 
charide groups contained in the molecule is not known 



222 APPLIED CHEMISTRY 

as is indicated by the formula. Cellulose is represented 
by the same empirical formula, but probably the value 
of n is different from what it is with the starches. It 
would seem possible, judging from the formulas of 
starch and cellulose, to convert such waste products as 
sawdust, which is largely cellulose, into a monosaccha- 
ride, as starch is made into glucose. No method, how- 
ever, has ever been devised which is cheap enough, al- 
though experimentally it is entirely possible. When 
dry starch is heated to 250° C. it is converted into a 
product called dextrin; when made into a paste, it is 
used instead of mucilage extensively, especially upon 
envelopes, stamps, and for similar purposes. It is also 
employed largely in sizing paper, weighting cloth, paper 
for cardboard, and for sizing walls preparatory to paper- 
ing. Paper is made from wood, straw, and various other 
articles which consist largely of cellulose. Another organic 
compound in the wood, known as liguin, is first removed 
by treatment with sodium hydroxide or some other chemi- 
cal reagent, and the remaining cellulose washed thoroughly 
with water. The pulp is then rolled into sheets and dried. 
Filter paper is nearly pure cellulose. 

Exercises for Review 

1. What is an ester? How did it receive the name? Name 
three. 

2. What is glycerol? Formula? Where obtained? 

3. Name four esters of glycerine. 

4. Of what does butter consist? What is mazola? 

5. What is oleomargarine? What advantages do the cocoa-nut 
oleos have? 

6. .What is a compound lard? Name some on the market. 

7. Write the structural formula of butyric acid to show it is a 
saturated compound. 

8. JSTame four olefins. How are they different from the paraf- 
fins? 



ETHEREAL SALTS, OILS, FATS, SUGARS 223 

9. How does olein cliff er from stearin? 

10. What is meant by hydrogenation? What effect does it have 
on an oil? Can stearin be hydrogenated? Why? 

11. What is a carbohydrate? Name three classes with example 
of each. 

12. What is "karo"? How made? 

13. Name three disaccharides. What is the origin of lactic acid 
in milk? 

14. How is cellulose different from starch? 

15. How is dextrin made? Uses? 

16. Of what does paper consist mainly? 



CHAPTER XIX 

POODS AND THEIR BODY VALUES 

Outline — 

Classes of Foods 

Carbohydrates 

(a) Sugars 

Starches 
(c) Cellulose 
Oils and Pats 

teins 
Minerals 

1. Kinds of Foods. — The various foods used may be 
classified as carbohydrates, oils and fats, and proteins, 
to which some add inorganic or mineral foods which 
may be made to include water. 

2. Carbohydrates. — The carbohydrates most commonly 
used as foods are the various sugars, starch and cellu- 
lose. AVhen sucrose, a general term for either cane or 
beet sugar, is boiled in the presence of an acid, it is 
slowly changed into glucose and fructose, both mono- 
saccharides, called hi this case, invert sugars. The proc- 
ess is called inversion. As the Invert sugar obtained is 
not as sweet as the cane sugar used, in stewing any acid 
fruit for table use it is better not to add the sugar till 
the fruit is about done. By this plan less inversion takes 
place and less sugar is required to render the fruit pal- 
atable. Xot only do acids have the catalytic action of 
inverting sugar, but certain enzymes as well. In our 
foods before sucrose is assimilated by the body it is con- 
verted into invert sugar by the enzymes of the diges- 
tive fluids. The sugars and starches serve mainly as 

22-1 



FOODS AND THEIR BODY VALUES 225 

fuel and energy producers. Since they contain suffi- 
cient oxygen to convert the hydrogen present into wa- 
ter, it is the carbon content alone that determines the 
relative fuel value of a carbohydrate. In the body it 
combines with oxygen obtained through the lungs and 
heat results, just as if so much carbon in the form of 
coal were burned in a stove. 

Starchy foods are obtained mainly from the various 
grains, wheat, corn, rice, rye, oats and barley; also from 
the potato, tapioca, arrowroot and sago. Bananas con- 
tain about 22 per cent of carbohydrates, much of which 
before the fruit is fully ripe is in the form of starch. 
When starchy foods are toasted, a portion of the starch 
is converted into dextrin, as is the outer portion of the 
crust of bread in baking. It is sweeter than starch, 
more soluble and more easily digested. All starchy 
foods, before digestion can take place, must be hyclro- 
lyzed or converted into invert sugar: this is partly ac- 
complished in mastication through the action of the 
enzymes in the saliva. The equation shows the change, 
which is altogether catalytic, 

C 6 H 10 O 5 + H 2 O-> C 6 H 12 6 . 

Used in the body carbohydrates serve two purposes, 
giving energy for muscular exertion and warming of 
the body. When assimilated into the circulatory sys- 
tem they meet the oxygen and chemical union takes 
place, accompanied by heat. Any excess may be stored 
up in the muscles and liver in the form of an animal 
starch called glycogen. This may be used whenever an 
insufficient amount is furnished by the daily food. 

Cellulose is found in many of our foods and is a car- 
bohydrate as seen in the preceding chapter, but it is 
no1 an energy producer, for the reason that it is not 



226 APPLIED CHEMISTRY 

digestible. It is the enclosing wall of starch granules; 
it is abundant in the stems of plants. As maturity is 
reached in many vegetable foods, the quantity of cellu- 
lose increases. This is seen in asparagus, string beans. 
turnips, beets, celery and various others. It is what is 
spoken of as crude fiber in grains ; the outside cover- 
ing of wheat, corn, unpolished rice and other cereals. 
It is not capable of inversion by any of the enzymes of 
the body and for that reason, as stated above, is indi- 
gestible. Nevertheless, it plays a far more important 
part in digestion and the bodily health than most of us 
realize. It serves as a stimulant to the secretion of 
the fluids necessary for digestion and excretion and 
aids in increasing peristaltic action ; in other words, it 
is a body-regulator food. Domestic animals such as 
the horse and cow use large amounts of what is called 
"roughness'' or hay, much of which is cellulose. Fed 
on concentrated foods entirely they lose appetite and 
quickly become a prey for all sorts of diseases. In all 
probability a large proportion of the bodily ills of man- 
kind may be traced directly to the use of foods too 
much refined and lacking in crude fiber or cellulose. 
Herein lies the health value of graham and bran breads 
and whole wheat foods and others of similar character. 
Pectin is another vegetable carbohydrate found in the 
juices of many fruits and in the inner portion of the 
peeling of the orange and other citrus fruits. It is 
the principle involved in the making of jellies. It is 
coagulated by acids and also by sugar. In boiling fruit 
juice the water is removed and the pectin concentrated. 
The point is finally reached where coagulation takes 
place upon cooling. This is determined by the house- 
wife by frequently testing small portions in a dish. 
For years numerous attempts were made to prepare 



FOODS AND THEIR BODY VALUES 227 

jellies from the cheaper grades of oranges regarded as 
unsalable by the packing houses, but all without suc- 
cess. Finally, it was found that in the orange the pectin 
is contained in the white portion of the peeling and 
not in the juice. Therefore when this portion is used 
with the juice of the fruit the operation is successful; 
and orange jelly and marmalade are now common arti- 
cles of commerce. 

3. Oils and Fats. — These foods are also heat and en- 
ergy producing. One pound of this class is about the 
equivalent of 2% pounds of carbohydrates. This is 
because the amount of oxygen contained is much less in 
proportion in the fats and oils. They produce heat and 
energy in the same manner as the carbohydrates. In 
good assimilation any excess of such foods is stored up 
as glycogen in the liver, or as adipose tissue in various 
parts of the body, presumably to be used in cases of 
forced abstinence or as other needs might come. 

4. Protein Foods. — Proteins are primarily muscle 
builders and not energy producing. It is true they may 
serve as body fuel, but as. nitrogen is not oxidizable, 
they are poor in this respect and should never be used 
with this idea in view. The body contains about 18 per 
cent of proteins. Whenever work is done, or muscular 
exercise of any kind is taken, some of the cells of the 
tissues are torn down and must be replaced. Plants have 
the power of building their own protein from the carbon 
dioxide inhaled from the air together with the nitrogen 
and water absorbed from the soil. Some few, the leg- 
umes, through the aid of bacteria, may even obtain the 
needed nitrogen from the air. But no animal has such 
power. It must use, for replacing wasted muscular tis- 
sue, protein already formed; this may be cither of ani- 
mal or vegetable origin. Such foods as eggs, lean meat. 



228 



APPLIED CHEMISTRY 



milk, cheese, beans, peas and other legumes are rich in 
protein. Several grains also furnish considerable pro- 
tein if the whole of the grain is used. As protein serves 
mainly to restore wasted muscular tissue, the amount 
needed depends upon the amount of bodily exercise 
taken. In general, it may be said that not over 3 ounces, 
80 grams, per day, are necessary, often much less. 
Those with sedentary employment require but little, 
while those engaged in manual labor need much. Too 
little regard is paid to this fact, with serious results 
to the bodily health. When carbohydrates are oxidized 
in the body, carbon dioxide and water are the sole prod- 
ucts and these are eliminated largely through the lungs. 
Proteins, being nitrogenous foods, are converted into 
urea, (NH 2 ) 2 CO, and this is eliminated through the 
perspiratory glands and by the kidneys. In case of ex- 



TABLE OF FOOD VALUES OF CERTAIN NUTS 
From Farmer's Bulletin, No. .332 



Nut 


WASTE 

% 


WATER 


PRO- 
TEIN 


PAT 


Carbo- 
hydrate 


FUEL VALUE 

PER POUND 

CALORIES 


Pecans 


50 


3.4 


12.1 


70.7 


12.2 


3325 


Hickorv 


62 


3.7 


15.4 


67.4 


11.4 


3240 


Walnut 


59 


3.4 


18.2 


60.7 


16.0 


3100 


Oocoanuts 


35 


13.0 


6.6 


56.2 


22.6 


2825 


Peanuts 


27 


7.4 


29.8 


43.5 


17.1 


2625 


Chocolate 


— 


5.9 


12.9 


48.7 


30.3 


2770 


Cocoa 


— 


4.6 


21.6 


28.9 


37.7 


2255 



SOME DRIED FRUITS 



FRUIT 


WASTE 

% 


WATER 


PRO- 
TEIN 


FAT 


Carbo- 
hydrate 


CALORIES 


Dates 


10 


15.4 


2.1 


2.8 


78.4 


1575 


Raisins 


10 


14.6 


2.6 


3.3 


76.1 


1560 


Figs 





18.8 


4.3 


0.3 


74.2 


1435 


Prunes 


15 


22.3 


2.1 


— 


73.3 


1370 


Apples 




28.1 


i.e. 


2.2 


66.1 


1320 



FOODS AND THEIR BODY VALUES 



229 



SOME FRESH FRUIT 



FRUIT 


WASTE 

% 


WATER 


PRO- 
TEIN 


FAT 


Carbo- 
hydrate 


CALORIES 


Banana 


35 


75.3 


1.3 


0.6 


22.0 


450 


Grapes 


25 


77.4 


1.3 


1.6 


19.2 


435 


Plums 


5 


78.4 


1.0 


— 


20.1 


380 


Cherries 


5 


80.9 


1.0 


0.8 


16.7 


355 


Pears 


10 


84.4 


0.6 


0.5 


14.1 


285 


Apples 


25 


84.6 


0.4 


0.5 


14.2 


285 


Orange 


27 


86.9 


0.8 


0.2 


11.6 


235 


Peach 


18 


89.4 


0.7 


0.1 


9.4 


185 



FOOD VALUES OF CEREAL PRODUCTS 



NAME 


WATER 

% 


PRO- 
TEIN 


FAT 


Carbo- 
hydrate 


CALORIES 


Crackers 


5.9 


9.8 


9.1 


73.1 


1875 


Rolled Oats 


7.7 


16.7 


7.3 


66.2 


1800 


Shredded Wheat 


8.1 


10.5 


1.4 


77.9 


1660 


Graham Flour 


11.3 


13.3 


2.2 


71.4 


1630 


Macaroni 


10.3 


13.4 


0.9 


74.1 


1625 


Hominy 
White Flour 


11.8 
12.8 


8.3 
10.8 


0.6 
1.1 


79.0 

74.8 


1610 
1610 


Rice 


12.3 


8.0 


0.3 


79.0 


1590 


White Bread 


35.0 


9.1 


1.6 


53.3 


1200 


Graham Flour 


35.7 


8.9 


1.8 


52.1 


1180 



FOOD CONTENT OF CERTAIN VEGETABLES 





WATER 


PRO- 




Carbo- 




NAME 






FAT 




CALORIES 




% 


TEIN 




hydrate 




Sweet Potato 


20 


1.8 


0.7 


27.4 


560 


Irish Potato 


20 


2.2 


0.1 


18.4 


380 


Parsnips 


20 


1.6 


0.5 


13.5 


295 


Onions 


10 


1.6 


0.3 


9.9 


220 


Beets 


20 


1.6 


0.1 


9.7 


210 


Carrots 


20 


1.1 


0.4 


9.3 


205 


Turnips 


30 


1.3 


0.2 


8.1 


180 


Cabbage 


15 


1.6 


0.3 


5.6 


145 


Cauliflower 


— 


1.8 


0.5 


4.7 


140 


Spinach 


— 


2.1 


0.3 


3.2 


110 


Celery 


20 


1.1 


0.1 


3.3 


85 


Cucumber 


15 


0.8 


0.2 


3.1 


80 


Green Peas 


45 


7.0 


0.5 


16.9 


455 


SI ring Beans 


7 


2.3 


0.3 


7.4 


190 


Squash 


50 


1.4 


0.5 


9.0 


210 


Tomatoes 


10 


0.9 


0.1 


3.9 


105 



230 APPLIED CHEMISTRY 

cess, uric acid forms and tends to accumulate in the 
muscles and about the joints and causes rheumatism. 
Those in sedentary employments, therefore, should use 
little meat or other nitrogenous foods. Nitrogenous 
foods in decomposing often produce what are called 
amines. These are substitution products of ammonia, 
one of which is NH 2 CH 3 , methyl amine. Some of these 
are very poisonous and are called ptomdins. In tables 
showing content of protein in various food products, 
the amount is often given in terms of nitrogen. As on 
an average the nitrogen in a protein is 16 per cent, to 
determine the amount of protein contained the nitro- 
gen must be multiplied by 6.25. The preceding tables 
show the food content and the fuel or calorific value 
of a large number of common articles of diet : 

5. Mineral Foods. — In all foods used there are small 
quantities of mineral matter or ash. These come from 
the soils and are taken up by the growing plant. While 
the amounts are small, certain portions seem necessary 
for health. The blood owes its color to the presence of 
iron compounds, and certain foods especially are rela- 
tively rich in these. Such are eggs, milk, peas, beans, 
figs, dates, raisins, wheat, rye, barley, and spinach. Cal- 
cium and phosphorus, usually combined as a phosphate, 
are especially needed in youth, but more or less at all 
times. The dry bone is over 50 per cent calcium phos- 
phate, while other portions of the body also contain 
smaller amounts. This must, therefore, be supplied. 
Such foods as milk, eggs, cheese, whole wheat, nuts 
and beans are rich in phosphorus. \Vhite flours are 
made by milling off the outer portions of the grain; 
hence, the cellulose and the mineral portions are lost 
as foods with serious consequences to the bodily health. 
In the body are also found sodium, potassium, magne- 



FOODS AND THEIR BODY VALUES 



231 



shim, chlorine and sulphnr. More than sufficient so- 
dium and chlorine are supplied in the common salt 
used. Sulphur is contained in such foods as eggs, and 
often in other protein foods. Magnesium and potassium 
are found in various nuts, cocoa, beans, peas, prunes, 




Fig. 47. — Foods rich in iron. (From Greer's Textbook of Cooking.) 
a, Peas; b, figs; c, wheat; d, lentils; e, spinach; f, dates; g, eggs; h, rye; i, 
beef; ;, beans; k, raisins; I, lima beans. 



figs, raisins, oats and rye. The following tables give 
the quantity of mineral matter contained in a number 
of common articles of diet. The value of water in the 
human economy has been discussed elsewhere. 

FOODS RICH IN IRON 
The following contain .003 per cent or more 
Beans, dry Lean beef Whole barley 

Dates Peas, dry Whole rye 

Eggs Raisins Whole wheat 

Figs, dried Spinach 

FOODS RICH IN PHOSPHORUS 
The following contain .9 per cent or more 
Beans, dry Cocoa Peas, dry 

Cheese Eggs, the yolk Whole wheat 

Chocolate Peanuts 



232 



APPLIED CHEMISTRY 




Fig. 48. — Foods rich in phosphorus. (From Greer's Textbook of Cook- 
ing.) a, Peas; b, chocolate; c, beans; d, peanuts; e, whole wheat; f, cheese; 
g, cocoa; h, yolk of egg. 

Figs. 47 and 48 show graphically what is given in the 
tables. (From Greer's Textbook of Cooking.) 
Exercises for Review 

1. K"ame the four classes of foods. 

2. What is meant by inversion? Why should the sugar be added 
after the fruit lias about finished cooking? 

3. Why is cellulose not digestible? Of what value is it to the 
body? What is meant by crude fiber? 

4. What is pectin? Of what practical value is it in the house- 
hold? Where is it found in most fruits? Any exception? 

5. What is the use of carbohydrate foods in the body? Why is 
a fat of greater fuel value than a sugar? 

6. Explain how the heat is produced in the body. How are the 
products of combustion in the body eliminated? 

7. Of what do protein foods consist? Name some typical ones. 

8. What value has a protein food to the body? How much of 
this kind of food is needed per day? 

9. Into Avhat is protein food converted when it has been used in 
the body? How is it removed? 

10. In case of excess of protein foods what is apt to follow? 
How remove this condition? 

11. Name the more common mineral foods. From what may the 
three most important be obtained? 

12. What do most "tonics" contain? What is the supposed 
purpose? 



CHAPTER XX 

SOLUTION AND IONIZATION 

Outline — 

Meaning and Kinds of Solution 
Concentration of Solutions 
Characteristics of Solutions 

(a) Change in Freezing Point 

(6) Eise in Boiling Point 

(c) Difference in Density 
Law of Variation 
Noted Exceptions 
Cause of Variation 
Conductivity of Solutions 
Dissociation 

(a) By Heat 

(6) By Solution 
Ionization and Ions 
Ions and Valence 
Ions and Chemical Action 

1. Definition of Solution. — As generally defined a so- 
lution is a homogeneous mixture of two or more sub- 
stances. Usually we think of it as a solid in a liquid, 
for snch are the more common. The solvent is the sub- 
stance of greater amount, while the solute is the other. 
Thus, if a few grams of salt be dissolved in a liter of 
Avater, the salt is the solute and the water is the solvent. 
There are several kinds of solutions besides that of a 
solid in a liquid. For example, air is a solution, in 
which the nitrogen is the solvent. Soda water is a 
solution of a gas, carbon dioxide, in water; a silver 
dollar is a solution of 10 parts of copper in 90 of silver. 
However, as solutions of solids in liquids are by far the 
most common, it is with them that this chapter deals. 

233 



234 APPLIED CHEMISTRY 

2. Solution Concentration. — The properties of solu- 
tions differ from those of the solvent. For the sake of 
comparisons it is necessary to agree upon some stand- 
ard when speaking of the strength of a solution. If a 
gram molecular weight of any substance be dissolved 
in a liquid so as to make one liter of the mixture, the 
solution is said to have a concentration of one, and is 
marked C ± . If a liter of a solution contains 2 gram 
molecular weights of the solute, its concentration is two, 
marked C 2 . Obviously, a gram molecular weight of sugar 
would contain the same number of molecules as a gram 
molecular weight of salt, although the former would con- 
tain 342 grams and the latter only 58.46 grams. So in all 
solutions with a concentration of one there would be the 
same number of molecules of the solute. 

3. Characteristics of Solutions. — As there is always 
a diminution of volume when two substances are mixed 
homogeneously, the specific gravity of the solution is 
always greater than that of the solvent. Again, the 
freezing point is always lower than that of the solvent, 
and the boiling point is higher, or, as it is usually ex- 
pressed, the vapor pressure is lowered. A little thought 
will make all three statements apparent. As a small 
handful of salt may be dissolved in a quart of water with- 
out greatly increasing the volume, evidently the water 
per cubic centimeter is heavier than before the salt was 
added. Heat is merely a form of molecular energy; 
when a body is warmed its molecules are made to move 
faster ; when cooled their motion becomes slower. There- 
fore, since there are more molecules in a given volume of a 
solution than in the same volume of the solvent, it would 
take more heat energy to set them in motion or, on the 
other hand, to stop them than if dealing with the pure 
solvent. In other words, speaking of cold as if it were 



SOLUTION AND IONIZATION 235 

a force, it would require a greater degree of cold to 
"slow down" the larger number of molecules in the solu- 
tion than it would the fewer number in the solvent, that is 
it is harder to freeze salt water than pure. Likewise, in 
bringing a solution to the boiling point, there would be 
more molecules to which there must be imparted a certain 
velocity before boiling begins, so the temperature would 
be higher before the boiling is reached. From the fact 
that a liquid begins to boil when the pressure of the 
vapor passing off from it equals or is slightly in excess of 
the atmospheric pressure above it, we usually say the 
vapor pressure is lowered instead of saying the boiling 
point is raised, but both expressions mean the same thing. 
4. Concentration and Freezing Point Lowering — 
Since all solutions with a concentration of one contain 
the same number of molecules of the solute per liter, 
it would seem from the kinetic viewpoint that the freez- 
ing point of all solutions, no matter what the solute, 
would be lowered the same for the same solvent. That 
is, if pure water freezes at 0° C. and a solution contain- 
ing a gram molecule of sugar per liter freezes at -1.8° 
C, we should expect a solution of alcohol containing 
a gram molecule per liter also to freeze at 1.8° below 
zero. Likewise we should expect such solutions with 
a concentration of two, that is with 2 gram molecules 
of the solute per liter, to freeze at -3.6°. If such experi- 
ments are made, using any of the soluble organic com- 
pounds mentioned in the preceding chapters, our ex- 
pectations are realized. These facts, then, are stated 
in this conclusion, that the lowering of the freezing 
point of a solution is directly proportional to the con- 
centration. Briefly it is expressed thus, 

L oc C, 
in which L means lowering of freezing point and C the 



236 



APPLIED CHEMISTRY 



concentration, and the sign, cc ? varies as. Experiments 
made upon the lowering of the vapor pressure of such 
solutions, show like results, so that the same formula 
may be applied to both cases. In tabular form below 
are shown some of the solutions commonly used with 
results upon the freezing point : 

TABLE OF FREEZIXG POINT LOWERING 



SUBSTANCE 


CONCENTRA- 


FREEZING 


GRAMS 




TION 


POINT 


PER LITER 


Alcohol 


C = l 


-1.8 


46 


Glucose 


C = l 


-1.8 


186 


Cane Sugar 


= 1 


-1.8 


312 


Glycerine 


C = l 


-1.8 


92 


Alcohol 


C = 2 


-3.6 


92 


Glucose 


C = 2 


-3.6 


360 


Cane Sugar 


C = 2 


-3.6 


684 


Glycerine 


C = 2 


-3.6 


184 


Alcohol 


C = 3 


-5.1 


138 



The results given above have disregarded slight varia- 
tions due to experimental errors or otherwise easily 
accounted for; they show conclusively what was pre- 
viously stated that the lowering of the freezing point de- 
pends upon the concentration. 

5. Exceptions to the Above, — It will be noticed that 
all the substances given in the table are organic com- 
pounds. "We should expect the same results, hoAvever, 
with the inorganic compounds, such as common salt, 
sulphuric acid, potassium chloride, and others familiar 
to us. When such are tried, using a concentration of 
one, the same as before, so as to introduce the same 
number of molecules per liter, the results do not agree 
at all. In some cases the freezing point is lowered 
nearly twice as much, in others nearly three times, and 
still others nearly four times as much as expected. 



SOLUTION AND IONIZATION 237 

6. Cause of This Irregularity. — It has been observed 
that chemical reactions between substances perfectly 
dry are practically nil. Pure dry hydrogen chloride does 
not react with zinc. It has been said elsewhere, Chapter 
I, that compounds, inorganic, are composed of an elec- 
tropositive and an electronegative portion and that each 
gives a separate test. In the absence of all water such 
tests cannot be made. With the organic compounds this 
is not true. They are not composed of a positive and a 
negative part and tests with them are tests upon the sub- 
stance as a whole. It seems then that when an inorganic 
compound is dissolved in water, in some way the posi- 
tive and negative portions are separated from each 
other so that each may be tested. Further, it was no- 
ticed that such compounds as common salt, potassium 
chloride, hydrochloric acid, ( ammonium chloride and 
many others, which were possible of separation into 
only two particles, one positive and one negative, always 
gave a lowering of freezing point almost double that 
of the organic compounds when concentration of one was 
used. Further, such compounds as calcium chloride, 
CaCl 2 , barium chloride, BaCl 2 , sulphuric acid, H 2 S0 4 , 
calcium hydroxide, Ca(HO) 2 and many others capable of 
breaking up into three portions, two positive and one 
negative or one positive and two negative, in concen- 
trations of one gave a lowering of freezing point nearly 
three times what the organic compounds did with the 
same concentration. Again, aluminum chloride, A1C1 3 , 
phosphoric acid, H 3 P0 4 , capable of breaking up into 
four parts, gave a lowering of the freezing point almost 
four times that given by the organic compounds in so- 
lutions of the same strength. From conclusions already 
reached in the case of the organic compounds, — namely, 
that the lowering is proportional to the concentration, 



238 APPLIED CHEMISTRY 

it came to be believed from the above observations that 
in water the inorganic compounds are broken up into 
parts and exist there not as molecules but as parts of 
molecules. If this be true, a solution of potassium chlo- 
ride, for example, would have as many particles to be 
1 ' slowed down ' ' in their movement as if the concentration 
were two; that is, the freezing point should be lowered 
3.6°. Likewise, such substances as sulphuric acid, or cal- 
cium chloride in solution would contain as many parti- 
cles as of the organic compounds with a concentration of 
three, and should give a lowering of 5.4°. 

7. Variation from Regular Lowering. — In all these 
cases, however, the lowering falls short of the theoretic 
amount, as shown by the following table: 

LOWERING OF FREEZING POINTS 

Substance Concentration Degrees Lowered 



Cane Sugar 


1 


1.8 


Grain Alcohol 


1 


1.8 


Sodium Chloride 


1 


3.5 


Calcium Chloride 


1 


5.1 


Aluminum Chloride 


1 


6.8 



Thus it will be seen that the greater the number of pos- 
sible particles into which the compound may be broken 
the greater the variation from the theoretic value. Ac- 
cording to the kinetic theory, not only are the mole- 
cules of a body in motion, but the atoms likewise in the 
molecule. Some years ago it was shown by the great 
Dutch chemist, van't Hoff that in dilute solutions the 
molecules of the solute are at such distances from each 
other that they obey all the gas laws. In these cases, 
therefore, the parts into which the molecules are broken 
would be moving in all directions, and in all probability 



SOLUTION AND IONIZATION 239 

would collide more or less frequently. For example, if 
potassium chloride is broken up into potassium and 
chlorine particles, in their movement the potassium and 
chlorine would more or less frequently collide and thus 
a molecule of the salt would be reformed. Among bil- 
lions of particles with a rapid motion these collisions 
would be frequent, so that there would always be, ex- 
cept in cases of very great dilution, a very apprecia- 
ble number of the molecules not broken up. Therefore, 
the number of particles in the solution, to be "slowed 
down," would never be quite double the number of the 
molecules, and, hence, the freezing point would not be 
lowered fully twice as much as in the case of the organic 
compounds. The same way with the calcium chloride, alu- 
minum chloride and others : there being more particles per 
degree of concentration, since each molecule may break up 
into three or four parts, collisions would be more frequent, 
more molecules would exist intact, and the lowering 
would vary further from three or four times the theo- 
retic amount. 

8. Conductivity. — It was long ago observed that such 
substances as sugar, and the organic bodies are not con- 
ductors of electricity, either by themselves or dissolved 
in water. It has also been seen that pure water is not a 
conductor. Inorganic compounds, which have been 
found to give very irregular results in lowering of freez- 
ing point, are not conductors when in the solid form, but 
dissolved in water are almost universally good conduc- 
tors. Such substances are spoken of as electrolytes, 
while those which will not conduct a current Avhen dis- 
solved in water are called twuelectrolytes. From the above 
observations and further, that when solutions of the inor- 
ganic compounds are electrolyzed the metal always ap- 
pears at the cathode and the nonmetal at the anode, it 



240 APPLIED CHEMISTRY 

was thought possible that the positive particles might be 
the means of conducting the current through the solution 
and of giving it up to the negative electrode. Further- 
more it was concluded that organic compounds are not 
conductors, because in water they are not broken up into 
particles so as to make it possible for one portion to be 
attracted toward the negative electrode. 

9. Dissociation. — It has been seen in a very consid- 
erable number of cases that at different temperatures 
substances may exist with molecules of differing com- 
position. Thus, nitrogen peroxide, at a temperature of 
about 23° C, has a molecular weight of 92, while at 
about 135° it is only 46, and at temperatures between 
these two it varies, being lower as the temperature is 
raised. As the molecular weight of 92 would correspond 
to the formula, N 2 4 , and 46 to that of N0 2 , there can 
be only one explanation and that is that heat decom- 
poses nitrogen tetroxide, and at a certain point this 
decomposition is complete, whereas at temperatures lower 
than this there are always present molecules of the 
greater density mixed with the lighter ones. This is 
shown by the equation, 

N 2 4 *± 2N0 2 , 

which means that the process is reversible and, what is 
more, is probably occurring at all times. When the 
temperature is lowered the reverse action is more rapid 
than the direct till a certain definite proportion is reached 
when equilibrium obtains. Such a reaction as this is 
called dissociation. Defined, dissociation is the decomposi- 
tion of a substance and the reforming of the same by the 
union of the products, when the decomposing cause is re- 
moved. Likewise, ammonium chloride, heated, decom- 
poses into ammonia and hydrogen chloride, but when the 



SOLUTION AND IONIZATION 241 

two gases are carried away from the source of heat they 
recombine to form ammonium chloride. Thus, 

NH 4 C1 ?± NH 3 + HC1. 

Again, iodine vapor, below 700° C. shows a density of 
about 127 compared to hydrogen or a molecular weight 
of 254, which indicates I 2 for the formula. Above 700° 
C. the density rapidly decreases and at about 1,700 it is 
only half what it was at 700. The same thing has occurred 
as in the case of the nitrogen peroxide and may be repre- 
sented thus, 

I 2 *± 21. 

Many others might be given. Such cases are spoken of 
as dissociation by heat. 

10. Dissociation by Solution. — As heat may be the 
means of dissociating substances, so it is believed liquids 
may be. When this occurs it is called dissociation by so- 
lution, or ionization. Because of the fact that dissocia- 
tion by solution permits of conductivity and the electroly- 
sis of the substance dissolved, it is often called electrolytic 
dissociation, but it must be remembered that electricity 
has nothing to do with the dissociation. Further, since 
in dissociation by this means the particles formed are 
able to be attracted to the electrodes of an electric cir- 
cuit, they are believed to be electrically charged ; hence, 
an equation representing the results of the dissociation 
of potassium chloride in water would be thus, 

KC1^K + C1, 
and of zinc sulphate, 

ZuSO , *± Zn + SO,. 

These electrically charged particles, whether atoms or 
groups of atoms, arc called ions, from a Greek word 



242 APPLIED CHEMISTRY 

meaning to travel. They were so named because of the 
fact of their constant movement from place to place. 
Ionization would be, therefore, the dissociation of a sub- 
stance into ions. 

11. Kind of Ions. — Ions are either positive or negative 
according to whether they are attracted to the cathode or 
the anode in an electrolyte. As already indicated, hydro- 
gen, ammonium and the metals may form positive ions, 
called cations or cathions, because they are attracted by 
the cathode: the nonmetals, hydroxyl, and many oxygen 
radicals, like -S0 4 , form negative ions, called anions, at- 
tracted to the anode. Ions are also spoken of as simple 




Fig. 49. — Ionization of a solution of common salt, and proof of same. 

and complex. A simple ion consists of a single atom, elec- 
trically charged, while a complex ion contains more than 
one atom, that is an electrically charged radical, like -HO. 
It must be remembered that ions are not atoms. A solu- 
tion of potassium chloride abounds in chlorine ions, but 
it possesses none of the properties of free chlorine — no 
color, no odor, no bleaching properties. The electric 
charge upon it, like an efficient rain coat not only pre- 
vents its "solution" in water, as it were, but also from 
doing the other things free chlorine would do. A very 
simple experiment shows the movement of the ions toward 
the electrodes in a solution. If salt water, colored with 



SOLUTION AND IONIZATION 243 

litmus cubes, be put into the U-tube, as shown in Fig. 
49, and the terminals of a battery be inserted, in a very 
short time the blue color at the anode will disappear. 
The chlorine ions have been attracted to this arm, and, 
coming- in contact with the positively charged carbon or 
platinum electrode, have lost the charge they held by 
having it neutralized. Now, they have become atoms of 
free chlorine. Immediately, they begin to bleach the 
litmus solution and decompose the water. Likewise, the 
odor of free chlorine becomes apparent as well as the 
color, if the process is continued long. If the salt water 
had been colored by a red litmus solution the anode arm 
would have been bleached as before while at the cathode 
the solution would have turned blue. The sodium ions 
move toward the cathode ; on meeting it they give up 
their positive charge to the electrode, become atoms of 
sodium, and immediately begin to decompose the water 
there. Thus, 

2Na + H 2 -> H 2 + 2NaHO. 

The hydrogen escapes in bubbles as can easily be seen, and 
the hydroxyl ions of the sodium hydroxide change the red 
litmus to blue. This, as has been stated elsewhere, is 
characteristic of all soluble hydroxides. Phenolphthalein 
is a coal tar product, which by soluble hydroxides is 
turned a beautiful violet-red color. In the above exper- 
iment, if a few drops of an alcoholic solution of phenol- 
phthalein be added to the salt solution instead of coloring 
with litmus, the solution at the cathode quickly turns 
pink, when the current is passed, showing the formation 
of a hydroxide just as before. 

12. Ions and Valence. — It will be noticed that the 

+ 
hydrogen ion was written above 11 while that of zinc 

was Zn. It will be found that the electric charge 



244 APPLIED CHEMISTRY 

upon an ion is the same as the valence. In making 
hydrogen, experimentally, it was found that one atomic 
weight of sodium displaces one atomic weight of hydro- 
gen from water and that one of zinc displaces two of 
hydrogen from acids. From this it would be seen that 
the valence of sodium is one and that of zinc is two. 
The ions, therefore, would carry single and double 

+ + + 
charges, respectively, Na, Zn. 

13. Chemical Action Ionic. — It has been seen that a 
piece of zinc dropped into pure dry hydrogen chloride 
liquefied, shows no chemical action, but if water be 
added it becomes vigorous immediately. Likewise, zinc 
in concentrated sulphuric acid in making hydrogen gives 
very indifferent results. Ferrous sulphide in concen- 
trated sulphuric acid shows almost no chemical action at 
all. In both of the last cases the addition of water 
brings vigorous results. It is believed from these and a 
very large number of other experiments, all indicating 
the same thing, that chemical action takes place between 
ions. In terms of the kinetic theory the presence of the 
water results in the ionization of the compounds, and 
the ions, moving through the solution in all directions, 
meet each other and form new combinations. Thus, 

KC1<=*K + C1, 
AgN0 3 ^Ag + N0 3 . 

If these two solutions are poured together collisions 
between the potassium and silver ions are impossible, 
because being with like charge, as they approached each 
other repulsion would take place ; likewise, the chloride 
ion and nitrate ion. But collisions between potassium 
ions and nitrate ions, also between chloride and silver 
ions could occur and would, as well as those indicated 



SOLUTION AND IONIZATION 245 

by the equations. But silver chloride is an insoluble 
compound, and hence could not ionize; therefore, as 
fast as silver chloride formed it would separate out from 
the solution. Ultimately, all the silver and chloride ions 
would have collided and been removed, at which time 
there would be solid silver chloride which would be 
in the form of a precipitate, potassium ions and nitrate 
ions, with some molecular potassium nitrate. 

14. Other Types of Reactions. — In the case just given 
one of the products is in the form of a precipitate and 
is thus removed from the sphere of action. The same is 
true if one of the products is a gas. Thus, if lime water 
is added to a solution of ammonium chloride, these 
steps would result, 

NH 4 C1 ±± NH 4 + CI, 
Ca(HO) 2 ^±Ca + HO + HO, 
NH 4 + HO <=> NH 4 H0, 

Ca + CI + CI <=t CaCL. 

Now if the solution is warmed as is done in preparing 
ammonia, the following results, 

NH 4 H0 -> NH 3 + H 2 0. 

Ammonia, being a gas, is constantly escaping, so that 
the ammonium hydroxide is being removed all the time. 
Therefore, the ammonium ions are being removed and 
the final result is calcium chloride in water ionized as 
shown by the equation, 

Ca + CI + CI ?± CaCl 2 . 

This is typical of all cases in which one product is a gas. 
There are many others in which all the products arc 



246 APPLIED CHEMISTRY 

soluble in water. Thus, when potassium nitrate and 
sodium chloride are mixed in solution, 

KN0 3 <=± K + N0 3 , 

NaCl *± Na + CI. 

Very shortly there would be some potassium chloride 
molecules and some sodium nitrate molecules from the in- 
evitable collisions ; but these products are both soluble in 
water and would both ionize, thus, 

KC1^K + C1, 

NaN0 3 <^Na + N0 3 . 

Evidently nothing is removed from the sphere of action 
in this case, and when equilibrium is reached, there are 
small amounts of all four compounds as well as large 
numbers of all four ions shown. Such chemical actions 
do not go to completion as is the case when one product 
is either a gas or a precipitate. 

15. Strong" Bases and Strong Acids. — Frequent use is 
made of the terms strong and weak acids and bases, and 
a clear understanding must be had. A strong acid or 
base is one that is largely ionized in solution. Since 
chemical action is between ions, where few ions exist there 
can be little action. Sulphuric, and hydrochloric are 
spoken of as strong acids; this simply means that in 
aqueous solutions they dissociate so as to produce a large 
number of hydrogen ions. On the other hand, such acids 
as carbonic and acetic are regarded as weak acids for 
the reason that in solution they are not ionized greatly. 
In concentrations of one, strong acids will be ionized 
fully 75 per cent, while weak acids not over one molecule 
in something over 50,000 is dissociated. The same is true 
of bases. Sodium hydroxide dissolved in water is largely 



SOLUTION AND IONIZATION 247 

broken into ions so that the quantity of hydroxide ion 
is large ; on the other hand, copper hydroxide is a weak 
base because of the portion which dissolves only compara- 
tively few of the molecules are ionized. 

Exercises for Review 

1. Define the terms solution, solvent, solute. 

2. Name seven kinds of solutions and give an example of each. 
What is the most common kind? 

3. What is meant by a concentration of one in a solution? Give 
examples. 

4. What is meant by a gram molecular weight of a substance ? 

5. Name three respects in which a solution differs from the 
solvent. 

6. Explain why the specific gravity of a solution is greater than 
that of the solvent. 

7. Explain by the kinetic theory why a solution has a lower 
freezing point than the solvent. Why should the boiling point be 
raised? 

8. What is meant by the expression, vapor pressure is lowered? 

9. What relation is there between lowering of freezing point and 
concentration of the solution? 

10. If 1 c.c. of a solution of sugar of concentration one con- 
tains a thousand molecules, how many would a solution of glucose 
contain if the concentration were the same? 

11. What kind of substances affect freezing point irregularly? 
Why is this? 

12. With a concentration of one, how much would a solution of 
potassium chloride lower the freezing point? CuS0 4 ? BaCLJ PtCl 4 ? 

13. To prove that a solution contained silver nitrate, how many 
tests would have to be made? For what? 

11. To prove that a solution contained alcohol, how many tests 
would be made? For what? 

15. Why does a solution of calcium chloride, CaCL,, not lower 
the freezing point three times 1.8, if it is capable of being broken 
into three particles? 

16. What is an electrolyte? Name five. Name five nonelectro- 
lytes. 

17. Why are electrolytes conductors? 



248 APPLIED CHEMISTRY 

18. What is meant by dissociation? Illustrate. 

19. Name two kinds of dissociation. What is ionization? 

20. Define ion. Name four kinds with examples of each. 

21. How is an ion different from an atom? Illustrate with the 
chloride ion. 

22. Give some experiment to show that ions are free to move. 

23. If alcohol were put into a U-shaped tube and the terminals 
of a battery inserted, what would collect at the anode? Cathode? 

24. AVhat relation is there between ionic charges and valence? 
Illustrate. 

25. When chemical change takes place in a solution between two 
substances, explain what really happens. 

26. Why does concentrated sulphuric acid not react with ferrous 
sulphide ? 

27. Write the ions formed by sulphuric acid in water; also fer- 
rous sulphide, FeS. Show by ionic equations what happens when 
they are put together. 

28. Write the ionic equations showing what happens when po- 
tassium bromide and silver nitrate are put together in a solution. 

29. What is meant by a reaction going to completion? Give two 
classes of reactions in which this happens. 

30. Knowing that barium sulphate is not soluble in water, when 
sodium sulphate, jNTa,S0 4 , and barium chloride, BaCL, are put to- 
gether, write the ionic equations and state whether the reaction 
would go to completion. 

31. What is meant by a strong acid? A strong base? Illustrate. 



CHAPTER XXI 
SULPHUR AND COMPOUNDS 

Outline- 
Occurrence of Sulphur 
Method of Preparation 
Characteristics 

(a) Physical 
( ~b ) Chemical 
Uses 
Compounds 

Hydrogen Sulphide 
The Oxides 
Sulphurous Acid 
Sulphuric Acid 

(a) Chamber Process 
(~b) Contact Process 
(c) Characteristics and Uses 
Thiosulphuric Acid 
Sodium Thiosulphate 

1. Occurrence in Nature. — Sulphur has been known 
from remote times. It is found free in abundant quan- 
tities in volcanic regions such as those of Sicily. Near 
the western entrance to Yellowstone Park vast quanti- 
ties in a free but impure form occur in what are known 
as the Sulphur Mountains. In Louisiana, at a distance 
of several hundred feet below the surface, are vast 
amounts of nearly pure sulphur, deposited in earlier 
ages probably through bacterial action upon sulphur 
compounds. Gypsum, calcium sulphate, as well as a 
large variety of other sulphur compounds, occur widely 
distributed, some of which may be used as a source of 
sulphur. 

249 



250 



APPLIED CHEMISTRY 



2. Method of Preparation. — At the present time Louis- 
iana furnishes by far the greater part of the sulphur 
needed by the United States. The process is very 
similar to that used for obtaining salt from underground 
deposits. Fig. 50 will make the plan clear. By drill- 
ing, a hole 6 or 8 inches in diameter is sunk until it 
reaches the sulphur deposit. Four concentric pipes are 
then inserted; through the two largest, water heated 
under pressure to a temperature of about 170° C. is 
run down upon the sulphur bed. Upon the innermost 



molten sulphur, 
air, and water 



water 
temp. no° 



^ A 

compressed 



i ii | 
I ll ,1 



II 



1 11,1 
I 1 ill 

'■I 1 !! 

hi in 



Fig. 50. — Method of obtaining sulphur in Louisiana. 



pipe pressure is secured by compressed air: in this way 
molten sulphur, hot water and air flow out through the 
remaining pipe into large bins. Here the sulphur solid- 
ifies while the water is conducted away. The sulphur 
thus obtained is sufficiently pure for all uses except 
those of medicine, and for shipment is blasted off with 
dynamite and loaded into cars. Formerly, about 90 
per cent of the sulphur used in the United States was 
obtained from Sicily. For pharmaceutic preparations 
further purification is deemed necessary. The sulphur 



SULPHUR AND COMPOUNDS 251 

is placed in retorts and heated to the boiling point; 
its vapors pass over into chambers where condensation 
takes place upon the walls or coarse sacking. This is 
in the form of a fine powder, known as flowers of sul- 
phur. If the process be continued for considerable time, 
the walls become sufficiently warm to melt the sulphur 
again and it runs to the bottom and is drawn off into 
moulds, in which form it is called brimstone or roll sul- 
phur. 

3. Physical Characteristics. — Sulphur is a solid of 
light yellow color. It is not soluble in water and is 
without odor or taste. It has a specific gravity about 
twice that of water and a melting point about 114. Its 




Fig. 51. — Sulphur crystals. 

best solvent is carbon disulphide in which at ordinary 
temperatures about 40 parts will dissolve in 100. If 
this solution be allowed to evaporate slowly, as may be 
secured by tying two or three thicknesses of filter paper 
over a beaker half or two thirds filled with the solution, a 
mass of beautiful crystals may be obtained such as are 
shown in Fig. 51. They are of the same shape as those 
found in nature but usually somewhat more perfect. They 
are called orthorhombic or octahedral crystals. Sulphur 
also forms long, needle-like crystals, known as mono- 
clinic. These may be obtained by melting a quantity of 
sulphur in a beaker or large test tube and pouring upon 
a filter paper in a funnel. In a short time the needles 
will be seen growing rapidly across the surface of the 
molten sulphur. At this stage the portion remaining 



252 APPLIED CHEMISTRY 

molten should be poured out, after which the crystals may 
be easily examined. The two varieties are of the same 
color, but in many respects are as dissimilar as oxygen 
and ozone. Monoclinic sulphur has a specific gravity of 
1.96, while that of the orthorhcmbic is 2.06 ; the former, 
a melting point of 119, the latter about 114; below 96° 
C. the needles break up into the orthorhombic. Hence, 
while a roll of sulphur recently made would consist of a 
massHf needle-like crystals closely intermingled, after a 
time these would have broken up into small octahedrons. 
On the other hand, if the orthorhombic variety be heated 
above 96° C. but not to the melting point, it slowly 
changes into the monoclinic variety. Sulphur brought to 
the boiling point and cooled suddenly, by pouring into 
water, forms another variety known as plastic or amor- 
phous sulphur. This is very dark brown in color and at 
first is soft and elastic and is not soluble in carbon disul- 
phide. In a few days it loses its dark color, and becomes 
hard and brittle. It is beginning to change back to the 
more stable variety. The process is very slow and may 
continue for years without completion. If put into water 
and kept at a temperature of 100° C. for about an hour, 
the change is complete. In heating sulphur to the boiling 
point, it is first a clear, golden-yellow, mobile liquid. As 
the temperature rises it becomes brownish in color, grow- 
ing gradually more viscous till it cannot be poured from 
the vessel containing it. At the boiling point, about 448°, 
it is again a thin liquid nearly black in color. 

4. Chemical Characteristics. — Sulphur above its kind- 
ling temperature reacts easily with oxygen, forming 
the dioxide. At red heat it combines vigorously with 
both copper and iron with the formation of sulphides. 
Sulphur vapor at a temperature not far above its boiling 
point shows a density indicating a molecular formula of 



Sulphur and compounds 253 

S 8 ; but like iodine and nitrogen peroxide, already stud- 
ied, as the temperature rises, the expansion of the gas 
and the specific gravity change much more rapidly than 
justified by Charles' law, and at 800° the molecular 
weight indicated is about 64, which is that demanded if 
the formula is S 2 , This gives another illustration of 
dissociation by heat, 

S 8 ±± 4S 2 . 

5. Uses of Sulphur. — While no longer used as exten- 
sively as formerly in medicine, sulphur still enters into 
a number of pharmaceutic preparations. It is mildly 
germicidal and is employed in some ointments for this 
reason. It is used extensively in viticulture in sprays 
to prevent the destructive effects of fungous diseases as 
well as upon rose bushes for the same reason. Boiled 
w T ith lime it is used upon peach, plum and other fruit 
trees to prevent "brown rot," a disease of fungous 
character. Very considerable amounts are used in the 
manufacture of matches, gunpowder and fireworks. One 
of the most extensive uses is in the manufacture of 
rubber goods. Without the addition of sulphur, native 
rubber becomes unduly soft in warm weather and brittle 
in cold. Vulcanite is hard rubber, obtained by heating 
ordinary rubber out of contact with the air to a consider- 
ably higher temperature. This form is familiar in pho- 
nograph records, combs, telephone receivers and mouth- 
pieces, electric insulation, fountain pens, and a great va- 
riety of other things. Lampblack is added in small 
amounts to give a black color : if pink is desired, vermil- 
ion is used. Considerable sulphur is used in the manu- 
facture of such compounds as carbon disulphide and 
sulphur dioxide. The former is a nearly colorless liquid 
of very unpleasant odor as usually obtained, and em- 
ployed largely as a solvent for various substances. 



254 APPLIED CHEMISTRY 

6. Compounds. — Sulphides. — Sulphur and oxygen be- 
ing members of the same family show much similarity in 
the compounds they form. Oxygen unites with all the 
common elements except fluorine ; so sulphur forms 
compounds with all the metals except gold and plati- 
num and with a very large number of the nonmetals. 
Nearly all the metals occur in nature as sulphides. 

7. Hydrogen Sulphide. — In nature hydrogen sulphide 
is often found in spring and artesian well waters. Eggs, 
which are proteins containing sulphur, in decomposing 
produce quantities of hydrogen sulphide, familiar to all 
in the exceedingly disagreeable, nauseating odor. In 
the laboratory it is obtained by treating ferrous sul- 
phide either with hydrochloric or sulphuric acid, con- 
siderably diluted, thus, 

FeS + H 2 S0 4 -* H 2 S + FeS0 4 . 

It is a colorless gas, a little heavier than air, with the 
well-known offensive odor of decomposing eggs. It is 
somewhat soluble in water with which it forms an acid 
solution, Jiydrosulphuric acid. It may be liquefied at 
about -60°. Hydrogen sulphide burns with a pale-blue, 
hot flame with the characteristic odor of burning sulphur. 
The equation is 

2H 2 S + 30 2 -> 2H 2 + 2S0 2 . 

If a cold dish be held against the flame, a deposit of sul- 
phur is formed. This shows that by the heat present the 
escaping hydrogen sulphide is dissociated to a greater or 
less extent, thus, 

2H 2 S <=> 2H 2 + S 2 . 

It is a very poisonous gas, producing dizziness, uncon- 
sciousness, and ultimately death. However, as at least 



SULPHUR AND COMPOUNDS 255 

y 2 of 1 per cent is necessary for fatal results, and as very 
much smaller proportions than this are distinctly notice- 
able on account of its very strong odor, serious results 
very rarely occur. It is said that very dilute chlorine, 
obtained by adding hydrochloric acid to bleaching pow- 
der solution, is the best antidote. It must be remembered, 
however, that chlorine is more poisonous than hydrogen 
sulphide; hence, when used as an antidote, great care 
must be exercised. Like carbon and carbon monoxide, 
hydrogen sulphide is a reducing agent. Hence, when 
bubbled through strong sulphuric acid, partial reduction 
of the acid results with the formation of sulphur dioxide, 
thus, 

H 2 S0 4 + H 2 S -* S + S0 2 + 2H 2 0. 

Hydrogen sulphide, therefore, cannot be dried by this 
method. Brought into contact with sulphur dioxide, a 
similar reduction takes place with the precipitation of 
free sulphur, thus, 

2H 2 S + S0 2 -> 2H 2 + 3S. 

This probably accounts in part at least for the deposits of 
sulphur in volcanic regions, as both the sulphide and 
oxide are produced by the action of heat upon compounds 
present in the earth. 

Dissolved in natural water, artesian or spring, hydro- 
gen sulphide is supposed to have therapeutic value, but 
this is very doubtful. In the laboratory, however, it is 
indispensable. It serves as the means of separating a 
large number of the metals into groups as the starting 
point of most chemical analyses. 

8. Sulphur Dioxide. — There are two oxides, sulphur 
dioxide and trioxide, but the former is the more com- 
mon. It is produced when either sulphur or hydrogen 
sulphide is burned in the air. In the laboratory it is 



256 APPLIED CHEMISTRY 

generally prepared by treating copper turnings or bits 
of charcoal with concentrated snlphnric acid, heated 
cautiously but somewhat strongly. It might be sup- 
posed at first thought that copper added to sulphuric 
acid would cause an evolution of hydrogen as zinc did. 
It will be found, however, by referring to Fig. 14 on 
p. 65 that copper is less strongly electropositive than 
is hydrogen, hence could not displace the latter from an 
acid. Moreover, we have seen that concentrated sul- 
phuric as used in this case gives but few hydrogen ions, 
and as chemical changes are usually between ions, a re- 
action similar to that between zinc and dilute sulphuric 
acid could not be expected here. Thus with zinc we had 

Zn + H 2 S0 4 -» H 2 + ZnS0 4 . 

Concentrated sulphuric acid, when heated, is an oxidiz- 
ing agent, that is, it gives up a part of its oxygen; in 
other words, in the present case the copper serves as 
a reducing agent in its reaction with sulphuric acid. 
It is not possible to prove that a certan chemical reac- 
tion takes place by steps, still it is entirely possible 
that in this case as in many others, such is true. On 
the above supposition, the first step in the reaction would 
be shown by the equation, 

Cu + H 2 S0 4 -^ CuO + H 2 + S0 2 . 

Then, secondly, CuO + H 2 S0 4 -> CuS0 4 + H 2 0. 
Adding the two equations gives the final result as it is 
known to be, 

Cu + 2H 2 S0 4 -> CuS0 4 + 2H 2 + S0 2 . 

9. Characteristics of Sulphur Dioxide. — Sulphur diox- 
ide is a colorless gas with a very suffocating odor. It 
is one of the easiest gases to liquefy; this may be ac- 
complished in any laboratory by surrounding a spiral 



SULPHUR AND COMPOUNDS 257 

tube connected with the sulphur dioxide generator with 
a freezing mixture of ice and salt. The liquid may be 
kept sealed hermetically in glass tubes, as the pressure 
at ordinary temperatures is only about three and a half 
atmospheres. The liquid if pure is nearly colorless, 
like water, and boils at -8° C. The gas is soluble in 
water to the extent of about fifty volumes in one and 
forms the unstable sulphurous acid, H 2 S0 3 , 

S0 2 + H 2 *=* H 2 S0 3 . 

It has a density compared to hydrogen of 32, hence is 
nearly two and a half times as heavy as air. Being an 
unsaturated compound, since the valence of sulphur is 
six, it has the power of taking up another atomic weight 
of oxygen for each molecule, and thus forms sulphur tri- 
oxide. 

10. Uses of Sulphur Dioxide. — Until comparatively re- 
cent years sulphur dioxide was used for disinfecting 
public buildings and homes in case of contagious dis- 
eases. The gas was secured by burning sulphur "can- 
dles" in the various rooms or where the ventilating fans 
would carry it to all parts of the building. As formalde- 
hyde is much more effective and more easily obtained 
it is largely supplanting sulphur dioxide for fumigating 
purposes. It is used extensively for bleaching various 
food products, as, for example, glucose syrups, already 
mentioned; also, for freshly cut fruits in drying. The 
fruit is peeled, cored and sliced, by machine at a single 
operation, and the slices spread upon trays over a fur- 
nace in an evaporator. A teaspoonful of sulphur is 
put into a cup on top of the furnace each time a double 
tray of fruit is inserted. The sulphur burns, forming 
sulphur dioxide, and the gas flows up over the fruit. No 
brown discoloration occurs as would be the case in pure 



258 APPLIED CHEMISTRY 

air, and in a very few minutes the fruit is dry upon 
the surface after which it remains perfectly white. In 
many localities in the West, fruits, especially peaches 
and apricots, are dried in the sun. To prevent attack 
by ants and other insects, the fruit after being cut is 
taken to a "sulphuring" room where it is exposed to 
sulphur dioxide fumes for a time. Sufficient is absorbed 
to protect the fruit in drying ; however, at the tempera- 
ture present, as the water evaporates, the sulphur diox- 
ide, except in minute traces, also disappears, so that no 
harmful results follow. The bleaching of English wal- 
nuts and almonds, possibly of some other nuts in Califor- 
nia, is a common practice. Lying upon the ground in 
the "hulls" as they may for some days before being 
gathered, the white shells become stained or mildewed, 
so that when finally shelled and dried they are of vary- 
ing shades of brown and gray. When taken to the 
packing houses, after being assorted into sizes, they are 
passed through a solution of bleaching powder to which 
dilute hydrochloric acid has been added, then carried 
by elevators to a "sulphuring" room, where they are 
exposed for some time to the fumes of sulphur dioxide. 
The result is a product with shells of a uniformly 
creamy-Avhite color. They are thus rendered pleasing 
in appearance without detracting from the wholesome 
character of the nuts. 

Liquefied sulphur dioxide is now an article of com- 
merce and is used extensively for bleaching woolens, 
straws and silks. Naturally, these articles are all of 
varying shades of yellow and woven thus are unattrac- 
tive in appearance. Chlorine is destructive of all such 
and cannot be used. Sometimes hydrogen peroxide is 
employed, but it is not so satisfactory as sulphur di- 
oxide. What the chemical action is when bleaching is 



SULPHUR AND COMPOUNDS 259 

done with this gas is uncertain. The other two bleaching 
agents already studied undoubtedly act by oxidation. As 
sulphur dioxide is an unsaturated compound it would 
presumably act by reduction of the colored compounds 
in the fabric to colorless. All such articles, on exposure 
to air and sunlight, again become yellow, caused possi- 
bly by their again taking up oxygen and returning to 
their first condition. Iceless refrigerators kept cold by 
the evaporation of liquid^sulphur dioxide are now being 
installed in many homes. The principle is the same as 
already explained in the manufacture of ice. 

11. Sulphur Trioxide. — This oxide has little interest 
outside the fact that it is the anhydride of sulphuric 
acid. It will be taken up in connection with the prepara- 
tion of that acid. 

12. Sulphurous Acid. — As already stated this acid is 
formed when sulphur dioxide is passed into water. It is 
unstable and of little importance. 

13. Sulphuric Acid.— Under the name, oil of vitriol, 
sulphuric acid has been known for centuries. It was 
formerly made, somewhat impure, by distilling ferrous 
sulphate, called green vitriol, which gave the name to the 
acid. At the present time two methods are used in its 
manufacture, the chamber and the contact process. The 
former is the older method, but the latter, where it may be 
applied is the cheaper. Both employ sulphur dioxide 
as the starting point. 

14. The Chamber Process.- — By this method the sul- 
phur dioxide needed is usually obtained by roasting 
iron pyrite, FeS 2 , which reacts with the oxygen of the 
air thus, 

4FeS, + 110 2 -» 8S0 2 + 2Fe 2 3 . 

The gas is passed into large chambers where it meets 



260 APPLIED CHEMISTRY 

nitric acid vapors prepared by the action of sulphuric 
acid upon sodium nitrate, thus. 

2NaN0 3 - H 2 S0 4 -* 2HN0 3 - Na 2 S0 4 . 

The nitric acid and the sulphur dioxide react, with the 
formation of sulphur trioxide and one or more nitrogen 
oxides, 

2HX0 3 + 3S0 2 -» 3S0 3 + H 2 - 2X0. 

Steam and currents of air are also introduced by which 
the sulphur trioxide forms sulphuric acid and the nitric 
oxide becomes peroxide, thus, 

H 2 0-S0 3 -* H 2 S0 43 

2X0 + 2 -> 2N0 2 . 

Only small quantities of nitric acid are needed, since it- 
serves merely as a catalytic agent to transfer the oxy- 
gen from the air to the sulphur dioxide. However, as 
four-fifths of the air is nitrogen which has no use in this 
process, in removing it special plans must be adopted 
to prevent loss of the nitrogen oxides also. The es- 
caping gases are made to pass up through what is called 
the Gay-Lussac tower, little more than a chimney with 
a lattice work of brick or tile, over which sulphuric 
acid slowly trickles. This acid has the power of com- 
bining with the nitrogen oxide present but not with the 
nitrogen, and forms what is called nitre acid or nitrosyl 
sulphuric acid. Thus, little of the nitric oxide is lost. 
The nitrosyl sulphuric is then pumped up to the top of 
another chimney known as the Glover tower and trickling 
down there meets the steam and fresh supplies of sulphur 
dioxide. The steam decomposes the niter acid forming 
sulphuric and sets free the nitric oxide which again com- 
bines with the oxygen of the air ; hence the process be- 
comes continuous. The chambers where the acid is pro- 



SULPHUR AND COMPOUNDS 



261 



duced are lined with lead, since it is not attacked by di- 
lute sulphuric. When it reaches a strength at which it 
begins to react with the lead, it is removed and further 
concentrated in stills made of cast iron or platinum. 
(See Fig. 52.) 

15. The Contact Process. — This process uses platinum 
as the catalytic agent. It is found that sulphur dioxide 
and air, mixed and passed through a heated tube, do 
not react to any appreciable extent. If finely divided 




ter Pot S Pyrites Burners 



Fig. 52. — Chamber process for sulphuric acid. The escaping gases pass 
up the Gay-Pussac tower where they meet the streams of sulphuric acid. 
This combines with the nitrogen oxide present, forming the niter acid, so 
called. This is pumped to the top of the Glover tower, where, descending, 
it meets the steam, which decomposes it. The nitrogen oxide then begins its 
work all over again. 



platinum be present, however, the union is rapid. In 
preparing the catalyzer, asbestos is dipped into a solu- 
tion of platinum chloride and heated. The chlorine is 
expelled and the finely divided platinum is left adher- 
ing to the surface of the asbestos. When this is heated 
and the mixed air and sulphur dioxide passed through 
it, sulphur trioxide is formed, which though a solid, 
is vaporized by the heat present and passes out of the 



262 APPLIED CHEMISTRY 

catalyzer into a receiver containing moderately dilute 
sulphuric acid, such as is obtained by the chamber proc- 
ess. This continues till the liquid becomes a white 
crystalline solid, known as fuming sulphuric acid, with 
the formula, H 2 S 2 T , or H 2 S0 4 .S0 3 . This indicates it is 
sulphuric acid saturated with the anhydride, sulphur 
trioxide. It might be supposed that the sulphur triox- 
ide obtained by the contact process would be passed 
directly into water, rather than into dilute sulphuric 
acid. The reason that this is not done is that the reac- 
tion is so violent that the heat produced volatilizes con- 
siderable portions of the trioxide with much loss. 

16. Characteristics of Sulphuric Acid. — When pure, 
sulphuric acid is a colorless, oily liquid, with a specific 
gravity of 1.84. It boils at 330° C. but considerable 
portions are broken up into sulphur trioxide and water. 
thus, 

H 2 S0 4 *± S0 3 -H 2 0. 

Sulphuric acid is strongly hygroscopic and exx^osed to 
the air rapidly increases in volume with corresponding 
dilution. When water is added, great heat is produced; 
hence, it is never safe to pour water into the concen- 
trated acid. The reverse order should always be fol- 
lowed. As already seen, this strong attraction for water 
is made use of in drying gases. When a pine splinter is 
dipped into concentrated sulphuric acid, it is charred, 
as is also a lump of sugar. From the former, being 
largely cellulose, C 6 H 10 O 5 the acid removes the hydrogen 
and oxygen as if it were water, leaving the carbon be- 
hind. The same is true of the sugar. In the diluted 
form sulphuric acid is largely ionized, hence is a good 
conductor of electricity, and with any metal more pos- 
itive than hydrogen readily reacts, giving off the hydro- 
gen. In concentrated form there are very feAV ions pres- 



SULPHUR AND COMPOUNDS 263 

ent; it is then a very poor conductor and with such 
metals as zinc and iron its reaction is very slight. 

17. Uses. — This is the most extensively employed of 
all acids. It is used in the preparation of all other acids ; 
the method for hydrochloric and nitric we have already 
seen. It is used in the manufacture of explosives such 
as nitroglycerine and guncotton, for the preparation of 
fertilizers from native phosphate rocks, in refining oils 
derived from petroleum and in the preparation of coal 
tar dyes. 

18. Thiosulphuric Acid. — This acid has never been 
prepared but its salts are well known. It has the for- 
mula, H 2 S 2 3 , which will be seen to be sulphuric with 
one of the atoms of oxygen replaced by one of sulphur. 
The first part of the word, thio, is from the Greek word 
for sulphur, and is given to this acid to indicate the fact 
of the substitution of the sulphur for the oxygen. One 
salt of this acid, sodium thiosulphate, is very important. 
It is sold under the name "hypo," formerly erroneously 
called hyposulphite of soda. It is used extensively in 
photography in "fixing" plates and prints so that they 
will not be further acted upon by the light. It is also 
used as an antichlor in the bleaching of textile fabrics to 
remove the last traces of the chlorine, so as to prevent its 
attacking the cloth. The fact that it was used during the 
later part of the war in gas masks has been mentioned 
elsewhere. 

Exercises for Review 

1. Name three localities where sulphur is found very abundantly. 
In what condition is it and how situated? 

2. Give the method of obtaining the supply used in the United 
States. 

3. Name four varieties of sulphur and state how each may be 
obtained. 



264 APPLIED CHEMISTRY , 

4. Give some important differences between the two crystalline 
varieties. 

5. Give the chief physical characteristics of sulphur. How does 
the amorphous differ from the yellow? 

6. What is an allotrope? What other substances have we met 
with in allotropic forms? 

7. Give the chief chemical characteristics of sulphur. 

8. Give some very important uses or" sulphur. What is vulcan- 
ite ? Uses. 

9. Where is hydrogen sulphide found in nature? Give some of 
its properties. 

10. Write the equation showing the combustion of hydrogen sul- 
phide. Why cannot it be dried by sulphuric acid as many gases 
are? 

11. What is meant by reduction? When hydrogen sulphide and 
sulphur dioxide are mixed, which is reduced, which is oxidized? Is 
it possible to reduce one substance without oxidizing another. 

12. Name the oxides of sulphur and give their formulas. 

13. How is sulphur dioxide prepared in the laboratory? How 
for fumigating? Why is hydrogen not obtained from the sul- 
phuric acid by copper? 

14. Give the chief properties of sulphur dioxide. 

15. Name the most important uses of sulphur dioxide. 

16. Name two other bleaching agents previously studied. For 
what are they used to bleach? 

17. Give the names of two processes for making sulphuric acid. 
How did it come to be called ' ' oil of vitriol 7 ' ? 

18. Describe briefly the chamber process and write the equations. 

19. Describe briefly the Contact process. What is the catalytic 
agent in each process? 

20. Describe the sulphuric acid and give some important uses. 

21. Why does a lump of sugar in concentrated sulphuric acid 
turn black? 

22. What is the action of sulphuric acid in making nitrocellu- 
lose? 

23. For what is hypo used? What is its chemical name? 



CHAPTER XXII 

PERIODIC CLASSIFICATION OF ELEMENTS 

Outline — 

Comparison of Metals and Nonmetals 

Atomic Weight and Chemical Characteristics 

The Periodic Table 

Valence in the Table 

Relation of the Properties to Position in Table 

Group Characteristics 

Numerical Relations 

Characteristics of Compounds as Related to Position 

1. Classification of the Elements. — Heretofore we have 
spoken of the elements as metals and nonmetals. Most 
of the common metals are of considerable density and 
lnstrons; but sodium and 'potassium are both so light 
as to float on water, yet are decidedly metallic in char- 
acteristics. Arsenic has a bright, metallic luster, yet 
can hardly be called a true metal. We have spoken of 
the metals as forming electropositive ions and the non- 
metals, electronegative: in a general way this is true, yet 
many of the metals are found in complex electronegative 
ions. Aluminum and tin are both metals, yet well known 
salts exist in Avhich with oxygen these metals constitute 
the negative ion. Likewise some nonmetals may form 
positive ions. The metals have been spoken of as form- 
ing basic oxides and the nonmetals as anhydrides. Gen- 
erally speaking, this is true. However, zinc hydroxide, 
Zn(HO) 2 , and aluminum hydroxide, Al(HO) 3 , are both 
soluble in sodium hydroxide, which indicates that the 
two bases must have ionized as if they were acids, thus, 

265 



266 APPLIED CHEMISTRY 

H 2 Zn0 2 <=> HH + Zn0 2 , 
H3AIO3 *± HHH + AIO3. 

This must be true for the salts formed are Na 2 Zn0 2 and 
Na 3 A10 3 , sodium zincate and sodium aluminate. It is 
seen, therefore, that there are many exceptions to the 
general statements regarding the two divisions of ele- 
ments hitherto used, such that this method of classifi- 
cation is far from satisfactory. 

2. Classification by Atomic Weights. — For long years 
there have been chemists who believed that the charac- 
teristics of an element bore some close relation to and are 
dependent upon its atomic weight. Various attempts 
were made to show this, but too many facts were un- 
known for any marked success. It remained for a great 
Russian chemist who died in 1907, to prepare what is 
known as the "Periodic Table" and to present the 
"Periodic System" in such a way as to cause its ac- 
ceptance by chemists at large. Starting with the idea 
that the properties of an element are a function of the 
atomic weight, Mendeleeff arranged the elements in the 
order of their atomic weights, beginning with the light- 
est, but omitting hydrogen. In this way he had lithium, 
glucinum, boron, carbon, nitrogen, oxygen, fluorine, 
sodium, magnesium, aluminum, silicon, phosphorus, sul- 
phur, chlorine, potassium, calcium, and so on. By in- 
specting this arrangement he discovered that leaving 
lithium, there is no other element similar to it until 
sodium is reached in the eighth space beyond, and then 
potassium another octave beyond the sodium. Starting 
with fluorine, no other element is met similar to it until 
chlorine is reached, the eighth beyond. Observing this 
fact in many instances, he next attempted to arrange the 
elements known to him into octaves, putting like elements 



PERIODIC CLASSIFICATION OF ELEMENTS 267 

under each other. To make the elements known at that 
time agree with his theory, he was compelled to leave 
many spaces in the table he prepared blank. But in doing 
so he predicted these spaces would be filled in the years 
to come ; what is more, he even foretold the general prop- 
erties these unknown elements would possess, their ap- 
proximate atomic weights, and, in some instances, actually 
suggested names for them. Most of his predictions have 
since that time been fulfilled, although the names he sug- 
gested have not been accepted. The latest form of the ta- 
ble, with some omissions as noted, as well as of some 
very rare elements whose position as yet is not deter- 
mined, is given on page 268. 

Only a very brief study of the table is possible at this 
time, but some knowledge of it is necessary and will be 
found very helpful to the student. Let it be remembered 
that the basis of arrangement is the atomic weights of the 
elements. 

3. Valence in the Table. — The vertical divisions in the 
table are called Groups and the horizontal divisions, Pe- 
riods. By looking at the top of each group, beginning 
with lithium, it will be seen that the valence increases 
from one up to seven. This is true for each period, with 
few exceptions which will be noticed. It is based upon the 
oxides which the elements form. For example, taking 
the second period, the respective oxides have the formu- 
las, Na 2 0, MgO, A1 2 3 , Si0 2 , P 2 5 , S0 3 , C1 2 7 . The 
next period, if the oxides are taken, shows the same va- 
lence, and so on through the table. If the hydrogen com- 
pounds are considered after the carbon group is passed, in 
which the valence is four, the apparent value decreases 
by one at each group. Thus, we have the formulas for 
the four compounds, marsh gas, ammonia, water and hy- 
drogen chloride, H,C, H 3 N, H 2 ? HC1. The following 



268 



APPLIED CHEMISTRY 





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PERIODIC CLASSIFICATION OF ELEMENTS 269 

periods show like valence with the hydrogen compounds. 
When Mendeleeff first prepared the table no element of 
the first column had been discovered and he made no 
plans for any such group. But strange to say, and won- 
derfully strengthening the probable truth underlying his 
plan, when the argon group was discovered one by one, 
with a slight exception to be noted, they all fitted into 
the general plan and no changes had to be made. Singu- 
larly, too, their valence is zero, that is they have no power 
of combining with other elements and as far as discovered 
form no compounds whatever. The slight exception to 
be noted is that argon as thus far prepared is slightly 
heavier than potassium, whereas it should be lighter. The 
probable explanation is that the argon thus far obtained 
is not pure but contains small quantities of one or more 
of the heavier gases belonging to the same group. It will 
be remembered that for years this was found true of the 
nitrogen obtained from the air ; and the fact of its un- 
seeming density when thus prepared led to the discovery 
of argon. One other exception which might be mentioned 
here is that iodine is slightly lighter than tellurium, 
whereas the reverse should be true. It is generally be- 
lieved that the weight of the iodine will sometimes be 
found to be slightly incorrect. Constant efforts are be- 
ing made to ascertain whether this may not be true. 

4. Position of the Elements and Properties. — It will 
be found that as we go from left to right in the table, 
omitting always the argon group, the elements become 
less and less electropositive and passing the carbon 
group, become more and more negative. Thus, sodium 
is very strongly positive while chlorine is equally 
strongly negative. Sodium forms a very strong base, 
chlorine a very strong acid. Taking the right hand 
end of the table it will be found, as we go down the 



270 APPLIED CHEMISTRY 

g*roup, that with the increasing weight the elements 
become less and less acidic in properties and begin to 
have some of the physical properties of the metals. 
Thus, in the halogen group, iodine is solid in form and 
has a luster, closely resembling that of most metals. In 
the nitrogen family the lightest one is a gas, phosphorus 
is a waxy solid, arsenic a brittle solid, but lustrous, 
antimony decidedly metallic in appearance but with 
some chemical properties of an acidic element, while bis- 
muth, the heaviest, is a metal both in appearance and 
behavior. Hence, instead of dividing the table into 
positive and negative elements by a vertical line near 
the center, it must be done by an irregular, or zigzag 
diagonal, starting at the left of boron, leaving it above 
and aluminum below the line, and so on through, leaving 
iodine above. Divided in this way the elements above 
the line generally speaking are electronegative or acid 
forming elements, while those below are positive or base 
forming elements. However, it must be further noted, 
that the elements near the irregular diagonal usually 
partake of a dual character and form both acids and 
bases, though weak ones. Thus aluminum, arsenic, an- 
timony, tin and others less familiar to the student all 
serve both as acid- and base-forming elements at dif- 
ferent times. 

5. Group Characteristics. — Taking any particular 
group for study it is found that all the members possess 
the same general characteristics and form similar com- 
pounds. We have thus noticed two members of the 
sodium group. Both are silvery white metals, light 
enough to float on water, decompose it readily even in 
the cold, are strongly caustic and form strong hydrox- 
ides. Taking the chlorine group, it is found that they 
resemble each other equally strongly. So it is found 



PERIODIC CLASSIFICATION OF ELEMENTS 271 

largely true throughout. Most strikingly is this ob- 
served in the chemical behavior and in the compounds 
formed. Thus, the sodium group forms no ordinary 
compounds of hydrogen for the reason that they are all 
strongly positive as is hydrogen also, but they do form 
oxides of the type, Na 2 0. The halogens form acids 
after the type, HC1. The sulphur group forms com- 
pounds with hydrogen seen in the formulas, H 2 0, H 2 S, 
H 2 Se, H 2 Te and with the oxides whose formulas are S0 3 , 
Se0 3 , Te0 3 . The nitrogen family forms hydrogen com- 
pounds shown in the formulas, NH 3 , PH 3 , AsH 3 , SbH 3 
and oxide compounds in N 2 5 , P 2 5 , As 2 5 , Sb 2 5 , Bi 2 5 . 
Hence, having learned the characteristics and com- 
pounds of one member of a group, we may know, in a 
measure that the same things are true of other members 
of the same group. 

6. Numerical Relations. — It was stated that Mende- 
leefO predicted with approximate accuracy the atomic 
weights of the unknown elements. By observation it 
will be seen that the atomic weight of any element is 
roughly speaking the arithmetic mean of those of the two 
adjacent elements. To illustrate : Sodium, weight 23, 
is one-half the sum of 7 and 39, the weights of lithium 
and potassium; scandium, weight 44, is half the weight 
of calcium and titanium, 40 and 48. Thus it is all 
through the table, although not always as exact as in 
these two cases ; but the variation is not great. 

7. Characteristics of Compounds Formed. — In a gen- 
eral way the character of the compounds may be known 
somewhat from the position of the elements forming 
them. Thus, nearby elements, possessing similar char- 
acteristics would not be expected to unite to form com- 
pounds at all. In the case of the metals, most of the 
unions formed are not true compounds. AVith the non- 



272 APPLIED CHEMISTRY 

metals, such as nitrogen and oxygen, nitrogen and chlo- 
rine, and others, when such do form compounds it is usu- 
ally through indirect processes by which the two ele- 
ments are left together and such compounds are very un- 
stable. The oxides of nitrogen already studied, are all 
more or less unstable; further, it has been noted that 
practically all the explosives are compounds of nitro- 
gen and oxygen and owe their explosive properties to 
the instability of such compounds. Chlorine and oxygen 
form oxides, indirectly, but they are dangerously explo- 
sive, as are also those of nitrogen and chlorine. On the 
other hand, elements distantly located in the table form 
very stable compounds. Thus, sodium and chlorine, or 
calcium and fluorine, unite readily and directly and form 
relatively very stable compounds. Such are a few of the 
more important facts regarding the periodic table. From 
this time forward the various elements studied will be 
taken up in accordance with the "Periodic System" or 
arrangement, as shown in the table. 

Exercises for Review 

1. What two divisions of the elements have been used thus far? 
Give some of the general characteristics of each division. 

2. What objection is offered to this as a scientific method of 
classification? 

3. What is the basis of arrangement in Mendeleeff 's table? How 
did he come to discover the recurrence of properties? 

4. What arrangement was made of the elements after the recur- 
rence of properties was observed? 

5. What is a group in the table? A period? 

6. State what is observed regarding valence in the table, using 
both the oxygen and the hydrogen compounds. What is the valence 
of the argon family? What is meant by that statement? 

7. State what is observed in passing from left to right in a 
period. 

8. What is true in each group at the right side of the table as 
the weight increases? 



PERIODIC CLASSIFICATION OF ELEMENTS 273 

9. Where does the dividing line come in the table? Give the 
general characteristics of the elements on either side of the line. 

10. What may be said of the elements close to the diagonal on 
either side? Illustrate. 

11. What is true of the general characteristics of the elements 
ir. any particular group? Illustrate by taking some family as that 
of sulphur or chlorine. 

12. What numerical relation exists among the elements? Take 
the entire first period and show this. 

13. What would be the approximate weight of the unknown ele- 
ment belonging in the space below caesium, in the sodium family? 
At the right of radium? At the right of molybdenum? 

14. What is generally true of compounds formed from elements 
near each other in the table? Illustrate. 

15. What is true of compounds formed from distantly placed 
elements? Illustrate. 

16. Why should arsenic be expected to have both basic and acidic 
properties? Which would be the more pronounced? 

17. Would you expect to find zinc with any acidic tendencies? 
If so, how would they compare with those of aluminum? 

18. Noting the fact that hydrogen and bromine are close to the 
diagonal, what would you expect to be true of the stability of hy- 
drogen bromide as compared with hydrogen chloride? What of 
hydrogen iodide? What does our work in bromine show? 

19. Ought chlorine to displace bromine from a compound or the 
reverse? How about chlorine and iodine? 



CHAPTER XXIII 

THE NITROGEN FAMILY 

Outline — 

Members of the Group 
Phosphorus 

(a) Occurrence 

( b ) Preparation 

(c) Forms of 

(d) Characteristics 

(e) Uses — Poisons 

Matches 
(/) Hydrogen Compound 
(g) Oxides 
(7j) Phosphates 
(i) Fertilizers 
Arsenic 

(a) Occurrence 

(b) Characteristics 

(c) Uses 
((7) Arsine 
(e) Tests for 
(/) Oxides of 

(g) Antidote for Poisoning 

(7i) Pigments 
Antimony 

(a) Characteristics 

(6) Uses 

(c) Stibine 

(<J) The Sulphide 

(e) Tartar Emetic 
Bismuth 

(a) Characteristics 

(&) Uses 

(c) The Nitrates 
Tabular Comparison of Compounds 
274 



THE NITROGEN FAMILY 275 

1. Members of the Family. — Nitrogen, the lightest, 
has already been studied in connection with the atmos- 
phere. The other members are phosphorus, arsenic, an- 
timony and bismuth. These four are all solids, and 
the last three, while not strikingly alike in some of their 
physical properties when untarnished, closely resemble 
each other in their bright metallic luster and crystal- 
line appearance ; but it is in the compounds formed and 
the chemical behavior in which they agree most closely. 

2. Phosphorus. — Phosphorus was discovered as long 
ago as 1669. About a century later, 1771, Scheele pre- 
pared it from bone-ash, a plan which has been followed 
nearly ever since. The word phosphorus means light- 
hearer, and was given to the element because of the fact 
that it glows in the dark when exposed to the air. In 
the form of a phosphate rock, calcium phosphate, it oc- 
curs abundantly in some of the Southern States, es- 
pecially Florida, South Carolina and Tennessee. It is 
found in small quantities in the nerve centers and muscles 
of the body, but more largely in the bones, of which, as 
calcium phosphate, it constitutes about three-fifths in 
weight. In the average human body it is said that there 
are about 3 pounds of phosphorus, nine-tenths of which 
is in the bones and most of the remainder in the muscles. 

3. Preparation of Phosphorus. — Up to recent years the 
bones of cattle, obtained from the packing houses, from 
which the gelatine and oil had been extracted, were 
charred to form bone charcoal. When this was no longer 
valuable for refining sugar, it was burned to a white 
ash in the air and from this calcium phosphate the 
phosphorus was distilled. At the present time, native 
phosphate rock, supposedly the fossil remains of birds, 
is mainly employed. With the crushed rock are mixed 
sand and coke or charcoal, the mixture 1 is fed into an 



276 



APPLIED CHEMISTRY 



electric furnace by a worm drive below the hopper, as 
shown in Fig. 53. When strongly heated the carbon re- 
moves a portion of the oxygen, while the sand forms a 
slag with the calcium and is drawn off at the bottom. 
The phosphorus, thus set free, distils out in the form 
of vapor, is condensed under ivater, and molded into 
small sticks. 

4. Forms of Phosphorus. — Similar to several other ele- 
ments already studied, especially, oxygen, carbon and 
sulphur, phosphorus occurs in two distinct varieties. 





Fig. 53. — Manufacture of phosphorus. 

Prepared, as described above, it is known as yellow 
phosphorus; if this be heated to a temperature of 250° 
C. out of contact with the air reel phosphorus is obtained. 
5. Physical Characteristics. — Yellow phosphorus, when 
freshly prepared or when first opened from a "tin" 
container which has excluded all light, is of a very pale- 
amber color, so nearly colorless, that it is sometimes 
called white phosphorus. It is of waxy appearance when 
cut. On exposure to light it deepens in color, owing to 
the formation of a coating of the red variety. The yellow 
is soluble in carbon disulphide, and taken internally is 



THE NITROGEN FAMILY 277 

very poisonous. The vapors, continually inhaled, are 
also poisonous, and produce a disease of the jaw bones, 
known locally as "phossy jaw," which may be relieved 
only by surgical operation and generally is incurable. 
The molecular weight of phosphorus vapor is 128, which 
indicates four atoms to the molecule, formula P 4 . Red 
phosphorus is a dark reddish-brown powder, not soluble 
in carbon disulphide. It is not poisonous and need not 
be kept in water as must the yellow. If vaporized at 
a temperaure of 300 it changes to the yellow variety; that 
is, the vapor from both the red and yellow varieties is the 
same and upon being condensed forms the unstable va- 
riety. 

6. Chemical Properties. — Yellow phosphorus, exposed 
to air, glows in the dark; in contact with chlorine it 
catches fire instantly; with liquid bromine, and after 
a few seconds with iodine, it does the same. If ignited, 
both varieties burn in oxygen with great brilliance. It 
is singular, however, that in a jar of oxygen, phosphorus 
does not glow at ordinary temperatures. If a solution 
of phosphorus in carbon disulphide be put upon two 
strips of blotting paper and inserted, one into a bottle 
of oxygen and the other into one of air, the latter will 
ignite as soon as the solvent has evaporated. The other 
remains unaffected unless the bottle be opened to the 
air when ignition takes place only after from one to 
three minutes have elapsed. 

7. Uses.— Yellow phosphorus in small quantities is 
used in poisons for rats, mice and similar vermin. Most 
of it, however, is employed in the manufacture of 
matches. The original sulphur match was made by dip- 
ping pine splints into molten sulphur, and then adding 
a mixture of phosphorus in glue. Friction exposed the 
phosphorus and ignited it, whereupon, the sulphur, of 



278 APPLIED CHEMISTRY 

low kindling point, caught fire and in turn the pine 
splint. Such matches, while, vastly better than none 
or those that had preceded them, burn slowly and form 
considerable sulphur dioxide. On this account they fell 
into disfavor. To increase the speed of combustion 
some oxidizing material, like potassium chlorate or ni- 
trate was added; instead of sulphur, the splints were 
dipped into melted paraffin for kindling. This gave 
a rapid match and a serviceable one, but dangerous. 
The mixture upon the head was too easily ignited; many 
fires were caused by the ordinary friction incident to 
their transportation. Moreover, owing to the amount of 
yellow phosphorus in their composition, not only were 
the workmen in the factories constantly subjected to the 
fumes, but children were often poisoned by them. These 
facts led to adverse legislation and in many states 
such matches were forbidden ; then came matches of 
the "Birdseye" type, which contained phosphorus only 
in the tip of the head and which could not be ignited 
by friction on the sides. These did away with most 
of the fires, but not with the poisonous properties. Fi- 
nally, the United States government by levying a direct 
tax of 2 cents per hundred matches legislated them out 
of existence. At present, ordinary matches are made 
by dipping the splints into melted paraffin for kindling, 
then into a mixture of some compound of phosphorus and 
some oxidizing material, as potassium chlorate, with dex- 
trin or glue as the adhesive. The friction produced by 
"striking" the match is sufficient to decompose the phos- 
phorus compound, ignite the phosphorus and then the 
kindling. The phosphorus compound used is not poi- 
sonous. 

8. Safety Matches. — In this variety of match red phos- 
phorus and antimony trisulphide mixed together are put 



THE NITROGEN FAMILY 



279 



upon the box by means of a little glue : upon the splint 
is the paraffin for kindling, and antimony trisulphide 
with some oxidizing compound. Friction upon the pre- 
pared surface of the box vaporizes a small portion of the 
red phosphorus, the vapor is ignited and sets fire to the 
combustible material upon the splint. Such matches may 
be ignited upon other surfaces, not thus prepared, but 
a long stroke, with much friction is needed to produce 
sufficient heat to ignite the antimony compound which 
is combustible. 




Fig. 54. — Preparation of phosphine. 

9. Phosphine. — This compound is a gas made by the 
reaction of a solution of either sodium or potassium hy- 
droxide upon yellow phosphorus. It is of interest be- 
cause of the fact that as thus obtained it ignites spon- 
taneously on exposure to the air. The following equa- 
tion shows the chemical reaction, 

P 4 + 3NaHO + 3H 2 -> 3NaHP0 2 + PH 3 . 

The reaction takes place at the boiling temperature, 
only slowly at room temperatures; the spontaneous ig- 



280 APPLIED CHEMISTRY 

nition is said to be due to the presence of a minute quan- 
tity of a liquid hydrogen phosphide, P 2 H 4 . If the 
gas be collected over water and allowed to stand thus 
for several hours, the liquid, P 2 H 4 , is dissolved and 
the gas does not ignite spontaneously. Apparatus 
such as was used for making hydrogen, may be used, 
except that the thistle tube should have substituted for 
it a piece of ordinary glass tubing bent at the upper 
end as shown in Fig. 54. This must reach to the bot- 
tom of the flask. Before applying heat the air must 
be removed; this is most easily done by attaching the 
gas supply to the bent tube and running the gas through 
for two or three minutes. The same should be repeated 
at the close of the experiment, otherwise as the air en- 
ters to take the place left by the contracting gas as it 
cools, it will cause an explosion. As the bubbles of phos- 
phine come to the surface of the water in the trough 
they ignite spontaneously and in still air rings of white 
"smoke" float upward. The gas has no practical uses. 
10. The Oxides. — Phosphorus forms two common ox- 
ides, the trioxide and pentoxide, P 2 3 , and P 2 5 , both 
produced by burning of phosphorus in the air. When 
the supply is plentiful, the higher oxide is obtained; 
when limited, the trioxide. They are both white solids 
and are the anhydrides of acids. Thus, 

P 2 3 + 3H 2 -> 2H 3 P0 3 , 
P 2 5 + H 2 ->2HP0 3 . 

The latter is very vigorous in chemical action such that 
when the oxide is dropped into water a hissing sound 
like that of a hot iron touching the water is heard. The 
acid produced is known as meta- or glacial phosphoric 
acid and corresponds to nitric acid, HN0 3 . If the pen- 



THE NITROGEN FAMILY 281 

toxide is put into boiling hot water the reaction is dif- 
ferent, thus, 

3H 2 + P 2 5 -» 2H 3 P0 4 . 

This is known as orthophosphoric acid. Upon heating, 
it loses water and changes into the metaphosphoric. 

11. Phosphates. — Salts of orthophosphoric acid are 
called phosphates. The most common are those of so- 
dium, potassium and calcium. These are found in most 
soils in sufficient quantities for plant growth, but suc- 
cessive cropping, especially by various grains such as 
wdieat or corn, remove them to such an extent that they 
must be replaced by fertilizers. The human body re- 
quires phosphates for the bones, muscles and nerve cen- 
ters. This is obtained mainly through the cereal foods, 
although eggs, beans and peas also contain it. 

12. Fertilizers. — The three things most needed for 
plants to insure vigorous growth and production of fruit 
or seed are nitrogen, phosphorus and potash. Means 
of procuring the nitrogen have already been studied. 
Two important sources of phosphates are the native rock 
already mentioned and bone products from the packing 
houses. Neither of these compounds is soluble in water 
and hence unavailable for plant food. However, if 
treated with sulphuric acid, they are converted into an 
acid phosphate, CaH 4 (P0 4 ) 2 , which is soluble in water 
and therefore suitable as a fertilizer. The reaction is 
shown thus, 

Ca 3 (P0 4 ) 2 + 2H 2 S0 4 -> 2CaS0 4 + CaH 4 (P0 4 ) 2 

Phosphorus-bearing iron ores are also a source of a con- 
siderable amount of the same acid phosphate, commercially 
known as the "superphosphate." It is said that in soils 
containing much humus the acids formed by the decom- 
position of the organic matter slowly convert native 



282 APPLIED CHEMISTRY 

phosphate into the superphosphate and thus make it 
available. 

13. Arsenic. — This element, third in density in the ni- 
trogen family, occurs in nature in arsenical iron pyrite 
(FeAsiS; also as realgar and orpiment. both sulphides 
of arsenic. The first named is the usual source of the 
commercial supply. 

14. Characteristics. — Arsenic as obtained from the py- 
rite is of a dark gray color, and as usually seen, not 
lustrous. Upon heating in an open dish the dull coat- 
ing disappears, leaving the element in its natural lus- 
trous, steel-gray color. It vaporizes upon heating without 
melting, at a temperature of 180 : C. The molecular 
weight of the vapor is 300 which is four times the atomic 
weight. This shows that the formula for the molecule, 
like that of phosphorus, is As 4 . Powdered arsenic sifted 
into a jar of chlorine ignites spontaneously and burns as 
it falls : on bromine, it combines likewise with vigor. In 
the air it burns with a purplish white light and forms 
heavy white fumes of the trioxide. As 2 3 . 

15. Uses. — There are few uses for the element. In 
the manufacture of shot from lead about 1 per cent of 
arsenic is added. The main reason for this is that the 
mixture of lead and arsenic is when molten much more 
limpid or mobile than pure lead. As a result, in pour- 
ing, the liquid is broken up the more easily and the shot 
are much more perfect. They are at the same time a 
shade harder than they would be otherwise. As the 
melting point of the mixture is lower than that of lead 
alone, solidification does not take place so rapidly, which 
gives the shot more time in assuming perfect spherical 
form. 

16. Arsine. — As nitrogen and phosphorus form hydro- 
gen compounds so does arsenic, with a formula corre- 



THE NITROGEN FAMILY Z8d 

sponding to that of ammonia and phosphine. It is usu- 
ally prepared by adding* to a hydrogen generator a so- 
lution of arsenic. It is usually not collected, but burned 
as generated. The equations show the chemical reac- 
tions taking place, 



Zn + H 2 S0 4 

AsCl 3 + 6H 



► ZnS0 4 + 2H, 
AsH 3 + 3HC1. 



In the equation it may be noticed that the hydrogen was 
not written H 2 as has been done in previous cases, when 
it has been collected in the molecular condition. In 




55. — Marsh's test for arsenic. 



the present instance it reacts with the arsenic as fast 
as it is set free from the acid and is said to be in the 
nascent condition. The term means being set free. In 
such condition it is much more active than in the molec- 
ular form. Some chemists offer a different explanation 
for the greater activity but the term is commonly used and 
should be understood. The arsine obtained thus always 
contains an admixture of hydrogen, but this does not in- 
terfere with the study of it. 

17. Characteristics. — Arsine is a colorless gas with a 
somewhat offensive and nauseating odor. It may be 



284 APPLIED CHEMISTRY 

liquefied at -40° C. It is exceedingly poisonous, so that 
small quantities inhaled may result fatally. It is easily 
decomposed by heat as shown by the equation, 

4AsH 3 -> As 4 + 6H 2 . 

This is easily shown experimentally. If a hard glass 
tube is attached to the arsine generator and a Bunsen 
flame is placed beneath the tube, the arsine is decom- 
posed; and at a short distance beyond the heated portion 
a black ring of the arsenic appears, while the hydrogen 
escapes from the tube and may be burned. The plan is 
simplified oftentimes, as shown in Fig. 55, by holding 
a cold dish against a small arsine flame. Brownish 
black spots with metallic luster appear upon the dish. 
The explanation is the same as before ; the vapor of ar- 
senic obtained by the dissociation of the arsine is con- 
densed in solid form upon the cold dish. This is usually 
spoken of as Marsh's test for arsenic, and is exceedingly 
delicate. The merest traces may be detected in this 
manner. The reaction when the arsine is burning freely 
in the air is, 

2AsH 3 + 30 2 -* 3H 2 + As 2 3 . 

The white fumes appearing are the trioxide of arsenic. 
When a cold dish is held in the flame, this equation 
shows what is happening, 

4AsH 3 + 30 2 -* 6H 2 + As 4 . 

The hydrogen continues to burn, but the arsenic vapors 
are condensed in solid form. In making this test precau- 
tion must be taken not to light the escaping gas until all 
the air is removed from the flask. A serious explosion is 
apt to result if this is not done. 

18. The Oxides. — There are two oxides of arsenic, the 
trioxide, As 2 3 , and the pentoxide, As 2 5 . The first is 



THE NITROGEN FAMILY 285 

much the more common. In commerce it is sold under 
three other names: arsenious acid, a misnomer, for it is 
merely the anhydride of arsenious acid, "white arsenic," 
and "arsenic." 

19. Characteristics of the Trioxide. — Usually it is ob- 
tained as a white powder, although occasionally as a 
colorless, glass-like solid. Like iodine, carbon dioxide 
snow, and elementary arsenic it vaporizes without melt- 
ing. It is slightly soluble in water and forms the corre- 
sponding acid, thus, 

As 2 3 + 3H 2 -> 2H 3 As0 3 . 

Taken internally it is a poison, but because of the fact 
that it is not very soluble it acts slowly. It is used 
very commonly as a poison for vermin and in large 
quantities in spraying apple trees to destroy coddling 
moth. For this purpose it is usually combined with lead 
acetate to form lead arsenite. This compound is the 
most desirable because on account of insolubility it is 
not washed away readily by rains and for the same rea- 
son does not "burn" the foliage. Arsenic trioxide is 
used to some extent in preserving skins in taxidermy 
and to a limited degree in medicine, especially Fowler's 
solution, a solution of the trioxide in potassium hy- 
droxide. 

20. Antidotes for Arsenic Poisoning". — The antidote 
most generally recommended for arsenic poisoning is 
freshly prepared ferric hydroxide. It is quickly made 
by putting together ferric chloride solution and ammo- 
nia water, taking care that the ammonia be not present 
in great excess. A heavy, brownish, flocculent precip- 
itate of ferric hydroxide is formed and this, filtered 
out, is used in a glass of water. The ferric hydroxide 
combines with the arsenic forming an insoluble com- 



286 APPLIED CHEMISTRY 

pound, which as a result cannot be absorbed by the sys- 
tem. An emetic or stomach pump should follow the 
antidote. Another sometimes used, which is easier to 
obtain but slower in action, is magnesium oxide, com- 
monly sold as magnesia. Its chemical action is the 
same as the ferric hydroxide. 

21. Paris Green. — This is rather a complicated com- 
pound as shown by the formula, Cu(C 2 H 3 2 ) 2 + 
CuHAs0 3 . It will be seen that it consists of copper ace- 
tate and acid copper arsenite, combined. Scheele's 
green is acid copper arsenite, CuHAs0 3 . Both com- 
pounds are bright green pigments and formerly were 
used extensively in coloring wall papers. Through the 
probable action of the decomposing paste upon the ar- 
senic compound, volatile compounds were produced 
which are very poisonous and serious results often fol- 
lowed. Coal tar dyes have uoav entirely supplanted these 
pigments for wall papers. Paris green is abundantly 
used in spraying or dusting potato plants to kill the Col- 
orado beetle. For small patches the powder mixed with 
flour or air-slaked lime is dusted upon the plants when 
wet with dew by means of a "shaker," homemade from 
a baking powder or similar can, by perforating the top 
with numerous holes. On a large scale the Paris green 
is usually mixed in water and sprayed on by pumps. 

22. Characteristics of Antimony. — In the nitrogen 
family antimony follows arsenic in density with an 
atomic weight of 120.2. It is a highly-crystallized, lust- 
rous, steel-white metal. Like arsenic it is very brittle, 
but does not tarnish as readily in the air. It has a 
melting point of about 445 and upon solidifying it ex- 
pands greatly. It combines readily with chlorine and 
bromine, and heated in the air, burns to antimony triox- 
ide. 



THE NITROGEN FAMILY 287 

23. Uses of. — Iii the form of antimony black, a very 
finely powdered or precipitated antimony, it is often nsed 
upon plaster casts to give them a metallic appearance. Its 
chief use is in alloys. By an alloy is meant an intimate 
mixture of two or more metals, melted together. They 
are generally really solutions, although some few are 
known which seem to partake somewhat of the nature of 
a compound. The more important alloys of antimony 
are brittania, pewter, babbitt, stereotype and type metal. 
The first two are alloys of copper, tin and antimony and 
are used mainly because they do not tarnish greatly in 
the air. Babbitt is used for bearings in machinery, as 
for example those of the crank shaft in motor cars, to 
reduce friction. Type metal consists of antimony, tin and 
lead and is of the utmost importance. The antimony 
causes the expansion of the type metal when it solidifies 
and thus gives sharp outlines to all the finest details. 
Made of lead alone, which contracts upon cooling, type 
would give prints entirely illegible. The purpose of anti- 
mony in stereotypes is the same. 

24. Stibine. — Antimony forms the hydride, SbH 3 , cor- 
responding to those of the members of this family al- 
ready studied. It may be prepared as was arsine. It 
may be liquefied at -18° C. It is even more easily dis- 
sociated by heat than is arsine and gives the same spots 
upon a porcelain dish as does the arsenic, although they 
are black rather than brown, more soft and velvety in 
appearance. If heat be applied, since arsenic is vola- 
tile, spots made by arsine will disappear, while the anti- 
mony will not. Further, a solution of bleaching powder 
will dissolve the arsenic spots and leave the antimony 
unaffected. 

25. Antimony Trichloride, SbCL. — This compound 
may be made by dissolving antimony in aqua regia. 



288 APPLIED CHEMISTRY 

It is sometimes called batter of antimony, because of 
the fact if not concentrated to the point of crystallization, 
it is an oily, yellow liquid, resembling melted butter. In 
the solid form it is white and crystalline. If water is 
added, partial solution takes place with the precipitation 
of a white compound having the formula, SbOCl, anti- 
mony oxychloride. The reaction is 

SbCl 3 + H 2 «± SbOCl + 2HC1. 

By cautiously adding hydrochloric acid and stirring, the 
reaction is entirely reversed ; upon adding more water the 
white precipitate again appears. It is an interesting case 
because it is one of the few in which reversibility is easily 
seen. 

26. Antimony Trisulphide, Sb 2 S 3 .— Found in nature 
this compound is steel-gray, about the color of lead. 
Prepared in the laboratory by passing a current of hy- 
drogen sulphide through a solution of some antimony 
compound, it is a beautiful orange colored precipitate 
which turns dark if melted. It is used extensively in 
the preparation of matches as previously stated. 

27. Tartar Emetic, KSbOC^Og.— From the formula 
this compound is seen to be basic antimony potassium 
tartrate. It is one of the few basic salts we have seen. 
It is a white solid and unlike the chloride is completely 
soluble in water. It is used somewhat in medicine as an 
emetic, but like all antimony compounds is very poison- 
ous. 

28. Characteristics of Bismuth. — Bismuth resembles 
antimony in general appearance in that it is highly crys- 
talline in structure, but its color is darker and of a pur- 
plish or golden luster. It is very brittle, much heavier 
than antimony with an atomic weight of 208. It melts 
at about 270° C. With chlorine and bromine its behavior 



THE NITROGEN FAMILY 289 

is about the same as that of antimony. Upon solidify- 
ing the metal expands greatly. 

29. Uses. — While it is eminently suited for type metal 
on account of its expansibility, being much more ex- 
pensive, it is rarely thus used, except in delicate stereo- 
types. One of its most important uses is in making 
alloys of low fusing point. Some of them are very re- 
markable in this respect. Thus : 



ALLOY 



Wood's Metal 
Eose 's Metal 



BISMUTH 



4 parts (270°) 
82 parts 



LEAD 



2 (325°) 
9 parts 



1 (232°) 
9 parts 



CADMIUM 



1 (320°) 
none 



MELT. PT. 



60.5°C. 

94°C. 



It will be seen that both these alloys melt below the 
temperature of boiling water, one of them much below. 
Thus, spoons cast of the former, if placed in a cup of hot 
tea or coffee would be melted and drop to the bottom. 
They are interesting illustrations of the fact brought 
out that solutions have their freezing point lowered. 
In these alloys bismuth may be regarded as the solvent 
with a freezing point of 270° C. for freezing point and 
melting point are the same. When the other metals are 
dissolved in this, the freezing point is lowered, in one 
case to 94° and in the other to about 60° C. This low 
melting property of bismuth alloys enables it to be em- 
ployed in a variety of interesting ways. Most city or- 
dinances require that the lanterns for moving picture 
shows be enclosed in a metal or fire-proof booth. The 
openings are provided with shutters held open by a 
chain one link of which is made of an easily fusible al- 
loy. In case of the film taking fire this link is easily 
melted, the shutter closes automatically and the fire is 
kept within the booth. Metal fire doors, between dif- 
ferent apartments in large manufacturing establish- 
ments, are often held open during the day by fusible 



290 APPLIED CHEMISTRY 

metal devices. In case of fire, the metal melts and the 
door is closed by the ordinary air spring attached. Au- 
tomatic sprinkling systems in large department and 
wholesale houses employ the same principle. Plugs in 
the pipes occur at intervals; if fire occurs they are 
melted and the water is turned on automatically. Steam 
boilers are likewise often provided with fusible plugs, 
such as to melt out and allow the escape of the steam 
before the danger point is reached. 

30. Compounds. — Not many of these are of sufficient 
importance to need attention here. The nitrate, 
Bi(X0 3 ) 3 , is a white crystalline solid, prepared by treat- 
ing bismuth with nitric acid. The reaction is thus 
shown, 

Bi + 4HN0 3 -> Bi(N0 3 ) 3 + 2H 2 + NO. 

When water is added a white precipitate forms of the 
basic or oxynitrate. 

Bi(N0 3 ) 3 + H 2 ±± BiOX0 3 - 2HX0 3 . 

Tested with litmus paper the solution is found to be 
acidic as is true also when antimony chloride is dis- 
solved in water. The reaction is also equally reversible, 
as may be shown by the cautious addition of nitric acid. 
This white precipitate is sold under the name "subni- 
trate" of bismuth and is used frequently in medicine, 
as a cosmetic and for stomach trouble. Bismuth forms 
no compound corresponding to those of arsine and stib- 
ine. 

31. Comparison of the Members of the Family. — Ni- 
trogen and phosphorus in their outward appearance at 
ordinary temperatures differ greatly from the other 
three. Nevertheless, nitrogen at low temperatures is 
a white solid and phosphorus nearly so. In their chem- 
ical behavior they are very similar in most respects. As 



THE NITROGEN FAMILY 



291 



stated elsewhere, as the elements in a group increase in 
weight, the tendency, seen best in the oxides, is to be- 
come basic or metallic in character. Thus the oxides 
of nitrogen and phosphorus are strongly acidic; of ar- 
senic, the trioxide has a double character, being both 
basic and acidic. It reacts with hydrochloric acid 
to form arsenious chloride, and with sodium hydrox- 
ide to form sodium arsenite. The pentoxide, As 2 5 , is 
acidic as might be expected with its higher percentage 
of oxygen. In the case of antimony, the trioxide is also 
of dual character, but more strongly basic than acidic, 
while the pentoxide is still acidic. With bismuth the 
trioxide is basic only. As further showing this same 
fact, nitrogen and phosphorus form no salts with these 
as the positive ions ; arsenic forms but few, not very sta- 
ble, antimony and bismuth many, especially the bismuth. 
The following table compares the several members in 
regard to other compounds not alread}^ named: 



Table For Comparison 





NITROGEN 
N=rl4 


PHOSPHOR- 
US 
P = 31 


ARSENIC 

As = 75 


ANTIMONY 
Sb — 120 


BISMUTH 

Bi — 208 


Hydrogen 
Compound 


Ammonia 

NH 3 


Phosphine 
PH 3 


Arsine 
AsH 3 


Stibine 
SbH 3 


None 


Oxides 


N a O, 

N, 2 0, 


p 2 o 3 

PA 


As.,0 3 
AsA 


SbA 
SbA 


BiA 
BiA 


Chlorides 


NC1 3 


PC1 3 


AsCl 3 (?) 


SbCl 3 


BdCl 3 


Oxychlorides 


NOC1 


POCl 




SbOCl 


BiOCl 


Acids 


HN0 3 


HP0 3 
Ii 3 P0 4 


H 3 As0 4 


H 3 Sb0 4 


None 



Exercises for Review 



1. Name the members of the nitrogen group. 

2. From what has phosphorus been mostly prepared? What in 
very late years? Give a brief outline of the process. 



292 APPLIED CHEMISTRY 

3. Name the forms of phosphorus. Compare them with sulphur. 
What other elements studied have been seen in allotropic forms? 

4. Give the characteristics of yellow phosphorus and compare 
with it the red. 

5. Which is the poisonous variety? "What disease do the vapors 
produce? What remedy is there for it? 

6. What is the chief use of phosphorus? Give another use. 

7. Give the various steps in the evolution of the common match 
as we have it to-day. 

8. Describe the safety match and state how different from the 
ordinary. 

9. How is phosphine made? What is the chief point of interest 
regarding it? What use has it? 

10. Name the oxides of phosphorus and give formulas. How 
prepared? 

11. Name two or three acids of phosphorus and state how they 
may be obtained from the oxides. 

12. What phosphates occur in nature? Of what use are they? 
How are they produced artificially for fertilizers? 

13. Give the chief characteristics of arsenic. 

14. Explain the jmrpose of the one use of arsenic. 

15. How is arsine made? How can you show that it is readily 
decomposed by heat? 

16. What is a nascent gas? How different from the molecular 
form ? 

17. Describe Marsh's test in full. 

18. Name the oxides of arsenic and give formulas. 

19. Describe the trioxide and give uses. What is the antidote 
for arsenic poisoning? Why may so much time be taken in pre- 
paring the antidote? 

20. AVhat two pigments of arsenic are common? What former 
\i se had they? Why no longer used this way? Chief use now? 

21. Give characteristics of antimony and compare with arsenic. 

22. What is antimony black? Use of it? 

23. Name the most important alloys of antimony and give some 
use of each? What is an alloy? 

21. Give composition of type metal and state wherein is its chief 
value. 

25. How is stibine made? How can its spot be distinguished 
from that made by arsine? 



THE NITROGEN FAMILY 293 

26. What is butter of antimony? How made? Why so called? 
When water is added to it, what results? Write the equation. 

27. What do you call an equation like the above? How can you 
prove that it is reversible? 

28. How is antimony trisulphide formed in laboratory? Of what 
practical use is it? 

29. Give use of tartar emetic. 

30. Describe bismuth and compare with antimony. 

31. Give chief uses of bismuth. 

32. Name two very fusible alloys of bismuth. Why do they have 
such a low melting point? 

33. Name two compounds of bismuth and state how prepared. 

34. Write the equation showing the reaction of water with the 
nitrate. 

35. What kind of an equation is this? How can you show ex- 
perimentally that it is reversible? 

36. Give a general comparison of the members of the group. 

37. Show how they become less acidic as they increase in weight. 

38. Compare the various oxides of the group in chemical 
behavior. 



CHAPTER XXIV 
COMPOUNDS OF SILICON 



Outline — 



Natural Compounds — Silica 

(a) Variety of 

(&) Characteristics 

(c) Uses 
Artificial Compounds 

(a) Water Glass 

(&) Crown Glass 

(c) Bohemian Glass 

(d) Flint Glass 
Manufacture of Glass Articles 
Annealing Glass 

1. Occurrence of Silicon. — Silicon belongs to the car- 
bon group. The latter element has already been stud- 
ied. Two metals, tin and lead, also belong to this group. 
They all have a valence of four. Next to oxygen, silicon 
is the most abundant of all the elements and constitutes 
something more than 25 per cent of the earth's crust. 
It is never found free as is carbon. In the combined 
form, sand, Si0 2 , is a very abundant mineral. Sandstone 
is the same with some cementing material holding the 
particles together. Crystallized, this same compound 
often occurs as hexagonal prisms; when transparent it 
is then called rock crystal. When delicately colored 
it is known as rose quartz, amethyst, milky, and smoky 
quartz, according to the nature of the coloring. Opals, 
agate, chalcedony, jasper, flint and onyx are other well- 
known varieties. Much of the agate is petrified wood; 
as the cells of the woody structure have been broken 
down in the process of very slow decomposition the sil- 

294 



COMPOUNDS OF SILICON 



295 



ica lias replaced them. The different colors are due to 
different compounds dissolved in the silica when it was 
deposited. The most noted of these petrified forests is 
near Adamana in Arizona. Here trunks of trees of all 
sizes, for the most part broken squarely across, are 
found in great numbers, covering many square miles 
in area. Many of the rocks constituting the crust of 
the earth are compounds of silicon. Such are kaolin, 




Fig. 56. — A scene in one of the petrified forests in Arizona. 

feldspar, and the clays resulting from the decomposition 
of the latter. Mica, which has the property of splitting 
into thin sheets, commonly used in stoves and often re- 
ferred to erroneously as isinglass, is a silicate. Granite 
is ordinarily a mixture of quartz, feldspar and mica. 
Pumice stone is a porous lava, used as an abrasive and 
in some washing powders, as "Dutch Cleanser." In- 
fusorial earth, spoken of in connection with the manu- 
facture of dynamite, is a porous, siliceous rock formed 



296 APPLIED CHEMISTRY 

from the shells of microscopic animals. Fig. 56 is a view 
of a portion of the petrified forests of Arizona. 

2. Characteristics of Silica. — If pure, silica is color- 
less. It ranks seventh in the scale of hardness, in which 
the diamond is tenth. It is not soluble in any acid ex- 
cept hydrofluoric, but is somewhat readily so in alkalies. 
Some of the hot springs in Yellowstone Park contain 
very considerable quantities of dissolved silica, so that 
articles left where the spray may fall upon them, or if 
dipped into the water repeatedly become covered with 
a silicious coating. Its melting point is so high that 
only the electric arc or the oxyhydrogen lamp is suffi- 
cient to fuse it. 

3. Uses of Some Forms of Silica. — The uses of sand 
for building purposes in mortar and cement are well 
known. For such work a coarse sand, with grains more 
or less rough, and not well polished, makes a much 
stronger wall or foundation. All glass requires sand 
for its manufacture ; sand papers of all degrees of fine- 
ness are made for polishing and smoothing wood sur- 
faces. Pure sand is now being made into crucibles and 
various other chemical apparatus, preferable in many 
ways to glass. As its coefficient of expansion is very low, 
it is much less liable to be broken by sudden great 
changes in temperature. The finer grained infusorial 
earths are used as abrasives for polishing metals, while 
sandstone is made into whetstones and grindstones for 
sharpening tools. The tinted varieties of quartz men- 
tioned are often cut and mounted in cheaper jewelry, 
where, owing to their hardness, they are very service- 
able. Lenses for optical instruments and spectacles are 
sometimes made from pure quartz. 

4. Silicic Acid. — Silicon dioxide, Si0 2 , is an acidic 
oxide as would be indicated by the fact that it combines 



COMPOUNDS OF SILICON 297 

so readily with alkalies. Theoretically, it is the anhy- 
dride of silicic acid, but as it is neither soluble in water 
nor reacts with it, silicic acid is not obtainable by di- 
rect means. Orthosilicic acid has the formula H 4 Si0 4 , 
but when precipitated from a silicate it loses a molecule 
of water and becomes H 2 Si0 3 . Many salts of these two 
acids are known. 

5. Water Glass. — When silica is fused with sodium 
carbonate, the following reaction takes place, 

Si0 2 + Na 2 C0 3 -> Na 2 Si0 3 + C0 2 . 

This sodium salt of silicic acid is generally used in the 
liquid form, or solution, somewhat resembling glycerine 
in appearance. If all water is removed, a transparent, 
colorless solid remains, closely resembling glass. In the 
viscous solution it is often called "water glass." At the 
present time very large quantities of it are used. It is 
probably the best preservative of eggs. For this pur- 
pose, a mixture of one part water glass and nine parts 
of water are put into a jar of suitable size. Into this are 
put the eggs from day to day, the fresher the better. It 
is well not to make up a very great quantity of the 
solution at one time, although there should be sufficient 
to keep the eggs covered. Any egg which floats in the 
solution should be discarded as it is already stale and 
may be the cause of spoiling others. Eggs decompose 
because of bacteria, which pass through the shell along 
with the air as it takes the place of the moisture which 
is being constantly evaporated. The water glass fills and 
closes the pores of the shell and thus prevents this inter- 
change. Eggs may be thus kept for months and are 
always far preferable to storage eggs even of less age. The 
jar and contents must be stored where the contents 
will not freeze, although a warm room is not desirable. 



298 APPLIED CHEMISTRY 

It may be remembered that the solution will have a 
freezing point much lower than that of water ; hence it 
will stand a considerable degree of cold. It is well to 
know that such eggs cannot be boiled without the shells 
cracking, as a rule. This is because at the boiling point 
the air contained would be greatly expanded ; because it 
cannot pass through the pores of the shells, it bursts 
them. After standing for some months a white gelati- 
nous mass will be found collecting in the bottom of the 
jar. This is silicic acid, and is formed as indicated by 
the equation, 

Na 2 Si0 3 + 2H 2 -> H 2 Si0 3 + 2XaHO. 

It has been said that water does not ionize and for that 
reason is not a conductor of electricity. It does, how- 
ever, ionize to a very sUglit extent, so that there are al- 
ways a few hydrogen and a few hydroxyl ions present in 
the water. Thus, 

H 2 <=± H + HO. 

Sodium silicate, being a salt, is largely ionized, thus, 

Na 2 Si0 3 *± Na,Na, + Si0 3 . 

Therefore, the hydrogen ions colliding with the silicate 
ions would form silicic acid, and as this is not appreciably 
soluble in water, it soon begins to separate out as a precipi- 
tate. This continues slowly and at the end of some months 
even an inch or more of white, gelatinous silicic acid may 
be found at the bottom of the jar. At the same time the 
hydroxyl ions meeting the sodium ions form sodium hy- 
droxide, but this being very soluble remains largely in 
the form of ions in the solution. This may be shown by 
testing with red litmus paper; it is also noticeable in 
its effect upon the hands, giving the skin a slippery feel- 



COMPOUNDS OF SILICON 299 

ing as alkalies all do. Such chemical action as this be- 
tween a salt and water is called hydrolysis, from two 
Greek words, meaning decomposition by water. Various 
other cases of hydrolysis will be studied later. In reality 
the action of water upon antimony and bismuth salts, ob- 
served in the preceding* chapter, is an instance of hy- 
drolysis. 

Water glass is also used as a cheap cementing mate- 
rial, in many cases taking the place of glue. This is 
seen in the manufacture of paper boxes, trunks, and 
valises. 

6. Crown Glass. — "When lime, sodium carbonate and 
silica are fused together, a double silicate of calcium 
and sodium is formed which is called crown glass. Un- 
less very pure sand is used there will be small quantities 
of iron present, which will give the product a green color. 
It may be largely removed by the addition of some oxi- 
dizing material like manganese dioxide ; but any slight 
excess of this compound imparts an amethyst color to the 
glass. Crown glass has a relatively low melting point ; 
hence, it may easily be softened in the Bunsen burner. 
It is also more readily attacked by alkalies than some 
other varieties. However, on account of its cheapness it 
is used for all ordinary bottles, for common window glass, 
and most of the test tubes and glass tubing used in the 
chemical laboratory. 

7. Bohemian Glass. — When potassium carbonate is 
fused with sand and lime a variety known as Bohemian 
glass is obtained. It is harder than crown glass, more 
transparent, less readily attacked by chemical reagents 
and has a much higher melting point. It is commonly 
spoken of in the laboratory as "hard glass." It is used 
for the better chemical glassware — beakers, flasks, and all 
sorts of other apparatus. The better grades of tumblers 



300 



APPLIED CHEMISTRY 



and other glassware in the home are also made from Bo- 
hemian glass. 

8. Flint Glass. — When sand, lead oxide and silica are 
fnsed together, a variety called flint glass is obtained. 
In the purest form it is sometimes called paste, and from 
it are made the imitation or paste diamonds. Flint glass 
is almost perfectly transparent, is very soft so that it is 
easily scratched, and has high refractive power. Most op- 
tical lenses are made from it on account of the ease with 
which it is cut, its brilliancy and high refractive power. 
It is the last property that gives the play of colors seen 
in the imitation diamonds, almost equal to the genuine; 
but the softness of the glass soon causes a loss of this 
power. It is also used in the manufacture of cut glass 
found in the home. 

9. Manufacture of Glass Articles. — Tumblers and sim- 
ilar articles of household use are molded. A sufficient 
amount of molten glass is put into a heated mold the size 




Fig. 57. — Mold for making glass tumblers. 



and shape of a tumbler. As shown in Fig 57, a rod de- 
scends, mechanically, bearing a solid but smaller 
tumbler. This squeezes the molten glass into the space 



COMPOUNDS OF SILICON 



301 



between the two and in a second of time the glass is 
done. Bottles are made by blowing. A suitable amount 
of molten glass is taken from the furnace upon the end of 
a blowpipe. (See Fig. 58.) This is placed within a mold, 
and by lung power or compressed air the glass is blown 
until it issues from the top of the mold in the form of a 




Fig. 58. 



■Mold for blowing glass bottles. The blow-pipe with molten glass 
is shown hanging within the opened mold. 



large bubble and bursts. Immediately, the bottle with its 
ragged top in placed in another machine which, while 
the glass is still soft, turns it round and round until 
the neck and top are perfectly smooth. Ordinary win- 
dow glass is first blown into long cylinders. These are 
cut lengthwise and flattened out while still hot, just as a 



!02 



APPLIED CHEMISTRY 



roll of paper might be with a pair of scissors. (See Fig. 
59.) Heavy plate glass is made by pouring a ladle of mol- 
ten glass upon a table and immediately rolling until it 
covers the top of the table and has attained a uniform 
thickness. It is then polished by revolving discs with 
water and pumice or some similar abrasive. The color of 




Fig. 59. — Making window glass. It is first blown into form of 
This is cut open, flattened out and annealed. 



cylinder. 



glass articles is secured by the introduction of small quan- 
tities of some other compound. It has already been stated 
that manganese gives an amethyst color ; cobalt gives 
a beautiful, deep blue; copper a lighter or greenish blue; 
chromium a clear, beautiful green; calcium fluoride a 
translucent white ; iron, pale green, yellow or brown, 



COMPOUNDS OF SILICON 303 

according to the kind of iron salt introduced; gold and 
some copper compounds give a red color. 

A glass rod kept soft by heat may be drawn out into 
thread and wound like silk fibers upon a large wheel or 
bobbin. From this it may be woven into various articles 
such as ribbons, bows for neckwear and even into cloth. 
Thus used it has the sheen of satin, but naturally it is not 
very durable. 

10. Annealing Glass. — All glass articles when first 
made are very brittle. Annealing consists in cooling 
them so very slowly that the molecules are enabled to 
move into relatively stable positions. This is done by 
putting the articles into a very long oven, one end of which 
is extremely hot. They are then very slowly moved 
mechanically toward the cooler end and after several 
days are ready for packing and shipping. 

Exercises for Review 

1. What can you say of the abundance of silicon compounds in 
nature? 

2. Name several varieties of quartz. 

3. Name several other minerals consisting of silica, some of 
which are prized for their beauty. 

4. What is petrified wood? How formed? 

5. Give the characteristics of quartz. 

6. Mention some uses for some of the natural forms of silica. 

7. What kind of an oxide is silica? What acid is formed theo- 
retically from it? 

8. How is water glass made? In what form is it used? 

9. Give method of preserving eggs with w/ater glass. 

10. Why do preserved eggs crack when boiled? 

11. What is meant by hydrolysis? Illustrate by means of so- 
dium silicate. 

12. Name two cases of hydrolysis in a preceding chapter. 

13. How r is crown glass made? Give some common uses for it. 
Why is it green in color? How may this be removed? 



304 APPLIED CHEMISTRY 

14. From what is Bohemian glass made? Give its differences 
from crown. 

15. What laboratory uses have these two kinds of glass, and 
why? 

16. From what is flint glass made? Give its most important 
uses. Why so used? What use has it in our homes? 

17. Give the common method of making tumblers. How are bot- 
tles made? Plate glass? Window glass? 

18. What is meant by annealing? How is it done? What is 
really accomplished by annealing? 



CHAPTER XXV 

THE ALKALI METALS 

Outline — 

Comparison of the Members 
Sodium 

(a) Occurrence 

(b) Method of Preparing 

( c ) Characteristics 

(d) Uses 
Compounds 

(a) Sodium Chloride 

(b) Sodium Bicarbonate 

(c) Sodium Carbonate 

(d) Sodium Hydroxide 

(e) Soap 
(/) Bo^ax 

(fj) Hydrolysis of Compounds 
Potassium 

(a) Occurrence 
(Z>) Characteristics 
Compounds 

(a) Potassium Carbonate 

(b) Potassium Hydroxide 

(c) Potass'um Nitrate 

(d) Potassium Chlorate 

(e) Other Compounds 

1. General Comparison. — This group includes the most 
strongly positive metals, as the halogen group does the 
most strongly negative. They occupy a position at the 
left end of the periodic table while the halogens are 
at the extreme right, The two important members are 
sodium and potassium ; the other three, lithium, caesium 
and rubidium, are much less common. More or less 
vigorously they all decompose water, forming strong 

305 



306 APPLIED CHEMISTRY 

bases or alkalies, for which reason they are commonly 
called the alkali metals. 

2. Occurrence of Sodium. — Common salt is one of the 
most familiar of all substances. It occurs in small 
quantities in nearly all soils; it is present in the dust 
particles floating in the air; it is the sodium in this 
compound which colors a flame yellow when a room is 
being swept. A clean platinum wire, drawn through 
the fingers, in a Bunsen flame will give the characteristic 
yellow coloration. It is found in the blood to the extent 
of 0.8 per cent. About seven-tenths of the solid matter 
found in sea water, or nearly 3 per cent by weight, is 
common salt, and amounts to the astonishing sum of over 
35,000 billion tons. Some one has calculated that on the 
basis of an average depth of 1,000 feet, the common salt 
in the various oceans would occupy a bulk of 3,500,000 
cubic miles and that if this were separated out and piled 
up it would make a mountain range rivaling in height 
and length some of our great western chains. In some 
of the Middle-West States, notably, Kansas, deposits 
of nearly pure salt are known, 300 feet in thickness, cov- 
ering vast areas. Likewise, Xew York, Ohio and Mich- 
igan have extensive deposits and these three states to- 
gether with Kansas furnish about nine-tenths of all the 
salt made in the United States. California, Utah, "West 
Virginia, Pennsylvania, Louisiana, Texas and Oklahoma 
also produce considerable amounts. In California one 
or more lakes covering an area of from 30 to 50 square 
miles are known, saturated with salt: a crust 6 to 8 
inches in thickness of nearly pure salt covers the surface 
over which in the dry season anyone may walk with 
safety. These lakes glisten in the sun like one in our 
northern climates, frozen over and covered with snow. 
Chile saltpeter, NaN0 3 , is another abundant natural 



THE ALKALI METALS 



307 



compound but not so widely distributed as common salt. 
It is found mostly in the desert areas of Chile, covering 
about 450 square miles or about the size of a single 
county in some of the Middle-West states. The deposits 
are from 25 to 50 per cent sodium nitrate and something 
like 5 feet in thickness, while the quantity is consider- 
able it is far from unlimited. Other natural compounds 
of sodium are known, but they are unimportant. 

3. Preparation of Sodium. — Sir Humphrey Davy, in 
1807, first prepared the metal by the electrolysis of so- 
dium hydroxide. At the present time the same method 
is used, improved, and known as the Castner process. 
Fig. 60 gives an idea of the apparatus. The sodium hy- 




Fig. 60. — Preparation of sodium by the Castner process. 



droxide is melted in a vessel, marked V, usually made 
of cast iron; to this is attached the cathode in the form 
of a bundle of carbon rods. The anode, marked W, is 
a vessel, similar to V, inverted over and dipping into 
the melted caustic soda. In the center, the vessel, P, 
which reaches down below the upper end of the carbon 
rods is the receiver for the sodium and is closed at the 
bottom by a coarse wire gauze. The current causes the 
sodium and hydrogen, both positive, to collect upon the 
carbon rods, from which they rise to the top within 
the vessel, P. The hydrogen escapes and the sodium 
when cooled is removed and molded into sticks. The 



308 APPLIED CHEMISTRY 

oxygen collects upon the vessel, W, which is the anode, 
from which it may be drawn off or allowed to bubble 
out and escape. 

4. Characteristics. — Sodium is a silvery-white metal, 
at ordinary temperatures soft and pliable. It reacts 
vigorously with water and must be kept under naphtha 
or some hydrocarbon oil free from oxygen. Exposed 
to the air it rapidly attracts the moisture, with which it 
reacts and forms sodium hydroxide. This in turn ab- 
sorbs the carbon dioxide and forms sodium carbonate, 
so that ultimately the metal when exposed to the air 
becomes a white, brittle mass. On a vessel of water at 
room temperature a piece of sodium rolls about, grad- 
ually diminishing in size, until it finally disappears. On 
warm or hot water the heat generated is sufficient to 
ignite the hydrogen evolved and volatilize small portions 
of the sodium which color the flame yellow. On wet 
blotting paper, a small bit of sodium, not able to roll 
around, soon becomes hot enough to melt, at a tempera- 
ture but little below the boiling point of water, 96° C. 
It is then a silver globule like mercury; if dropped 
upon the floor at this point it breaks into numerous 
smaller globules which burn with the usual yellow flame 
as they roll off in all directions. The irritating white 
fumes Avhich arise as the metal thus burns are sodium 
peroxide, Na 2 2 . Sodium is soluble in mercury, and if 
present in sufficient quantity forms a solid amalgam, 
an alloy of which one constituent is mercury. This 
readily decomposes water, but less rapidly than sodium 
alone. The fact is made use of in the electrolytic process 
of making chlorine described on p. 122. Sodium may be 
converted into vapor at about 750° C. The density of the 
vapor shows it to be monatomic. When heated sodium 
combines readilv with both oxygen and chlorine ; the oxy- 



THE ALKALI METALS 300 

gen compound thus obtained is the peroxide, spoken of 
elsewhere as "oxone" used in preparing oxygen. 

5. Uses. — Sodium has no commercial uses. In drying 
some organic compounds and in some other laboratory 
work it is of value. The. preparation of artificial rubber, 
still in the experimental stage, employs sodium in one 
step of the process. 

6. Compounds. — The occurrence of sodium chloride in 
nature has already been mentioned. It is obtained from 
these sources in two or three ways. A very consid- 
erable amount is mined as any other mineral. Since 
more or less insoluble foreign matter usually accompan- 
ies this rock salt as it is called, it is largely used for 
stock, or crushed to coarse grains for making freezing 
mixtures for refrigeration and for keeping ices and 
creams. At Salt Lake, Utah, the water, already satu- 
rated, is pumped into basins and evaporated by the heat 
of the sun. The product is somewhat impure but suita- 
ble for refrigeration and for packing purposes. At San 
Francisco the water is pumped likewise into basins and 
evaporated. Most of the salt used upon the table and 
in food products is obtained from salt wells. These are 
drilled down to reach the layer of salt, water is run in 
and allowed to remain until saturated. It is then 
pumped out and after any insoluble matter has settled 
out, it is evaporated and crystallized. 

7. Characteristics of Salt. — Salt obtained from wells 
is comparatively pure. Usually it contains a very small 
percentage of magnesium chloride which, being deli- 
quescent, causes the whole mass to become damp in wet 
weather. If a stream of hydrogen chloride be passed 
through a saturated solution of salt, pure sodium chlo- 
ride will separate out in fine crystals. As the mag- 
nesium chloride contained is usually less than 1 L > of 



310 



APPLIED CHEMISTRY 



1 per cent and most of the samples of salt upon the mar- 
ket assay from 97 to 99 per cent in purity, it is not nec- 
essary, except for some chemical purposes, to purify the 
commercial supply. At the present time several brands 
of table salt may be obtained which do not cake in 
damp weather. They have not been freed from the mag- 
nesium chloride, but have had some finely powdered sub- 
stance like starch or cooking soda or prepared chalk 
in very small amounts intimately mixed with the salt, 



fl^ -^ I,,, g " , _ H F t^jj^H^ . 4^ 


L^ # 




fS^GJlAM 






- 


; 



Fig. 61. — Preparation of salt in San Francisco Bay, by evaporation of sea 

water. 



so that the individual grains are protected from the air 
by a thin coating of the powder. It will probably be 
found, if the label upon the container is read, that the 
adulterant used will be stated. As the substance thus 
employed is harmless and always in very small propor- 
tions, it cannot be said to be especially objectionable. 
Upon the lower organisms salt is altogether destructive. 
Such is the explanation of its preservative qualities. 
Sprinkled upon such soft bodied animals as snails and 



THE ALKALI METALS 311 

slugs, which in some parts of our country grow to great 
size, salt seems to extract the moisture from the body. It 
shrinks rapidly in size, and the animal soon dies. In large 
amounts it is harmful to the human body, and in some 
countries has been frequently used as a means of suicide. 
In small quantities it is regarded not only as not harmful 
but even necessary for the body, to provide the hydrochlo- 
ric acid needed in digestion. Undoubtedly, however, 
nearly everyone uses much more than necessary, so that 
it must be eliminated by the skin in the perspiration and 
through other excretory organs. 

8. Uses. — It is said that about 11 pounds per capita of 
refined salt is used every year in the United States in the 
seasoning of foods. Much more is employed in the pres- 
ervation of meats and meat products. Altogether, sta- 
tistics show that the total quantity used every year 
in various ways amounts to 30,000,000 barrels, more than 
a barrel for every family of four individuals. Besides 
these uses, so familiar to all, salt forms the starting point 
in the manufacture of S3veral very important compounds 
which will be studied later. 

9. Sodium Bicarbonate. — This compound, chemically 
known as acid sodium carbonate with formula NaHCO s , 
is common cooking soda. The word bicarbonate means 
twice carbonated, and was so given because the compound 
was formerly prepared by passing a stream of carbon di- 
oxide into a solution of sodium carbonate, whereupon 
the bicarbonate, being much less soluble, crystallized out. 
Thus it was obtained by carbonating sodium carbonate. 
The equation shows the reaction, 

C0 2 + Na 2 CO s + H 2 -> 2NaHC0 3 . 

At the present time the commercial supply is made by 
what is known as the Solvay process. A saturated solu- 



312 APPLIED CHEMISTRY 

tion of salt is treated with ammonia and carbon dioxide 
when three reactions take place, thus, 

NH 3 + H 2 -> NH 4 H0, 
NH 4 HO + C0 2 -» NH 4 HC0 3 , 
NaCl + NH 4 HC0 3 -* NaHC0 3 + NH 4 C1. 

Aj i the acid carbonate is not very soluble in water it crys- 
tallizes, after which it is removed, dried and pulverized, 
usually, for the ccmmercial supply. The ammonium chlo- 
ride solution is saved, treated with lime and heated, 
whereupon the ammonia is recovered to be used again 
in the first step of the process. It will be seen, there- 
fore, that the manufacture is very cheap, 

2NH 4 Cl + CaO -* CaCl 2 + 2NH 3 + H 2 0. 

10. Sodium Carbonate. — The greater portion of the 
acid carbonate made by the Solvay process is converted 
into the normal carbonate by heating, thus, 

2NaHC0 3 -> Na 2 C0 3 + H 2 + C0 2 . 

The carbon dioxide thus obtained is used in the first 
step of the process described above for making sodium 
bicarbonate, which still further cheapens the process. 
Another method, known as the Leblanc process, was 
used for many years. This consisted in the conversion 
of common salt into sodium sulphate by strongly heat- 
ing with sulphuric acid during which reaction hydrogen 
chloride was evolved. (See p. 126.) By further treat- 
ment of the sodium sulphate thus obtained with coke and 
limestone the sulphate was converted into a carbonate 
which was separated from the mixture by dissolving 
in water. The process is much more complicated and 
expensive than the Solvay and would now be abandoned 
were it not for the by-product obtained, hydrochloric 
acid. By the Solvay process anhydrous sodium carbonate 



THE ALKALI METALS 616 

is obtained; by the Leblanc, the hydrate, Na 2 C0 3 . 10H 2 O. 
This is known as sal soda or washing soda. It is strongly 
efflorescent and when exposed to the air rapidly loses 
nine of the water molecules contained. Heat i< necessary 
to remove the remainder. Sodium carbonate is a neutral 
salt, yet, dissolved in water, it gives an alkaline reaction 
with litmus. This is explained in the same way as in the 
case of the water glass, p. 298. The sodium carbonate 
in water is largely ionized, thus, 

Na 2 C0 3? ±Na, Na + C0 3 . 
Water forms some few ions, 

H 2 ±± H +HO. 

The hydrogen ions reacting with the carbonate ions pro- 
duce carbonic acid. This, however, is an exceedingly 
weak acid, and, as is true of all weak acids, is very slightly 
ionized, hence exists almost entirely in the molecular 
form. The hydroxide ions reacting with the sodium form 
sodium hydroxide, which being a very strong base is 
largely ionized. Thus a very considerable amount of hy- 
droxide ion is always present in such a solution. As the 
alkali reaction is due to the presence of hydroxide ions 
a solution of sodium carbonate always turns litmus paper 
blue. 

11. Further Study of Hydrolysis. — As stated above 
the alkaline reaction of sodium carbonate is due to hy- 
drolysis. It is of such importance as to merit further 
study. Common salt dissolved in water shows no litmus 
reaction. The reason may be seen by writing the ionic 
reactions, 



NaCl 


^±Na 


+ C1 


H 2 0; 


=±H + 


HO, 



314 APPLIED CHEMISTRY 

When the ions present react, two new products form, 
NaHO and HC1. As one is a strong base and the other 
a strong acid they give relatively equal quantities of 
hydrogen and hydroxide ion and hence neutralize each 
other so that there is no litmus reaction. If sodium 
sulphate be used, like results are obtained, 

Na 2 S0 4 <=±Na, Na + S0 4 , 
H 2 *± H + HO. 
The new products are sulphuric acid and sodium hy- 
droxide, both strong. Again the hydrogen ions and hy- 
droxide ions practically neutralize each other and there 
is no litmus reaction. This is true of all salts formed 
by the union of a strong base and a strong acid. It is 
usually stated thus: Salts formed by the union of a strong 
base uniting with a strong acid are not hydrolyzed appre- 
ciably in tvater. 

Salts like sodium carbonate and sodium silicate are 
the result of the union of a strong base and a weak acid 
and give alkaline reaction. Conversely, salts formed from 
a weak base and a strong acid give an acid reaction. This 
will be evident if the ionic equations are written, 

FeCl 3 <=± Fe*+Cl, CI, CI, 

H 2 O^H-HO. 

The new products formed are hydrochloric acid and ferric 
hydroxide. The acid is very strong, while the base is 
weak; obviously, therefore, the litmus reaction will be 
acid in character. 

CuS0 4 ±± Cu + SO,. 

H 2 0^±H-HO. 
In the above solution the base formed will be copper hy- 



THE ALKALI METALS 315 

droxide which is weak and the acid sulphuric which is 
strong. Again the litmus reaction will be acid. All such 
salts behave in a similar manner. This case is usually 
expressed thus : Salts formed by the union of a weak base 
with a strong acid, or conversely, by the union of a strong 
base with a weak acid are partially hydrolyzecl. They 
give an acid or alkaline reaction according as the acid or 
the base is the strong factor. 

There is a third class of salts formed by the union of a 
weak base with a weak acid. Such are ferric carbonate 
and aluminum sulphide. Ionically written, ferric car- 
bonate gives 

Fe 2 (C0 3 ) 3 *± Fe, Fe + + C0 3 + C0 3 + C0 3 , 
H 2 +± H + HO. 
The ferric ions collide with the hydroxide ions and give 
ferric hydroxide ; likewise, the hydrogen and carbonate 
ions form carbonic acid. Both compounds are ionized 
very slightly. The result is the molecules accumulate; 
the solution becomes saturated with carbonic acid and at 
once it begins to decompose with the escape of carbon 
dioxide, thus, 

H 2 C0 3 ->H 2 + C0 2 . 

Thus the carbonate ions are constantly forming mole- 
cules of carbonic acid and this is being destroyed by the 
escape of the carbon dioxide, so that it is removed from 
the sphere of action. Likewise, the ferric hydroxide, not 
being appreciably soluble in water, begins to form a pre- 
cipitate and it also is removed from the sphere of reac- 
tion. The ultimate result is that practically all the car- 
bon dioxide escapes and the ferric ions have formed fer- 
ric hydroxide which alone remains as a precipitate. In 
other words, ferric carbonate in water has been converted 
entirely into ferric hydroxide, that is completely decom- 



316 APPLIED CHEMISTRY 

posed. The conclusion is usually stated thus: Com- 
pounds formed by the union of ei weak base with ei weak 
acid in water are completely hydrolyzed. The action of 
one class of baking powders depends upon this very 
fact and will be taken up at another time. 

12. Uses of Sodium Carbonate. — Its chief use is for 
the manufacture of other compounds. With silica it is 
used in making two varieties of glass ; it is also used in 
preparing sodium hydroxide, a very important com- 
pound to be studied later. It is used extensively in soft- 
ening water and is the chief constituent of most wash- 
ing poAvders. In addition, these may contain powdered 
caustic soda, borax, pumice stone, soap powder, sodium 
peroxide, and possibly sometimes some other substances. 
Scouring powders usually contain pumice; if put into 
a glass of water and stirred the other ingredients will 
dissolve leaving the pumice as a gray deposit. " Dutch 
Cleanser" is a washing powder of this kind. They are 
excellent in their way, but should not be used on highly 
polished surfaces such as silverware and the like. 

13. Sodium Hydroxide. — This compound. XaHO, is 
commonly called caustic soda. In an impure form it is 
frequently sold at groceries under the name of "lye." 
Much of it is prepared from sodium carbonate by treat- 
ing it with slaked lime thus, 

Ca(HO) 2 + Na 2 C0 3 -> CaC0 3 - 2XaHO. 

The calcium carbonate is not soluble in water, hence 
forms a precipitate from which the caustic may be 
drained off. A considerable amount of sodium hydrox- 
ide is also made electrolytically as described under 
chlorine. Made thus it is much more apt to be pure 
than by the other process; in fact, commercial caustic 



THE ALKALI METALS 317 

soda made from sodium carbonate often contains as 
much as 25 per cent of the latter compound or other im- 
purities. For most of its uses such impurities, however, 
are not especially objectionable. To obtain pure caus- 
tic soda from this commercial variety it is dissolved in 
alcohol, filtered and the solvent evaporated. The im- 
purities do not dissolve in the alcohol, hence are left 
behind in the filtration. 

14. Characteristics of Sodium Hydroxide.— It is a 

white solid : the pure caustic is usually sold in the form 
of small sticks although it may be had in a powder. The 
commercial variety is usually powdered. It is exceed- 
ingly caustic when moist, and is very deliquescent. Ex- 
posed to the air it rapidly dissolves in the moisture 
present, takes up carbon dioxide, and ultimately, as 
stated in the case of sodium, forms solid sodium car- 
bonate. 

15. Uses. — As already stated caustic soda is a constit- 
uent of many washing powders. It is used in the manu- 
facture of paper pulp, in decomposing the woody fiber; 
also in many other manufacturing processes. Probably 
its most extensive use is in the manufacture of soap. 

16. Soap. — Soap is a salt which in water gives an 
alkaline reaction because of hydrolysis. It is prepared 
by treating some fat or oil with caustic soda. The reac- 
tion is shown by the following equation, 

3NaITO + C 3 H 5 (C 17 H 35 COO) 3 -> 

3NaC ]7 H 3 ,COO + C 3 H 5 (HO) 3 . 

Stearin has been used here as typical of the other fats. 
It will be noted that glycerine is the by-product. On 
a large scale, soaps are generally made from the waste 
fats, or those of animals condemned by inspectors at 



318 APPLIED CHEMISTRY 

the packing houses as unfit for food, and from other 
similar sources; also from some of the cheaper oils. The 
yellow rosin soaps usually contain considerable rosin 
substituted for a portion of the fat. The chemical proc- 
ess in the making of soap is called saponification. Chem- 
ical reaction with organic compounds is nearly always 
slow, for the reason that they are not ionized. Hence, 
three or four days of constant boiling are necessary for 
the completion of the process. At the end of this time, 
salt is added, which causes a more perfect separation of 
the salt and glycerine. The salt water with the glycerine 
is drawn off beneath the soap layer, evaporated until of 
such concentration that the salt will crystallize out, after 
which the grycerine is concentrated in "vacuum pans" 
under partial air pressure. If potassium hydroxide is 
used instead of sodium, a soft soap is obtained in which 
the glycerine remains dissolved. In small quantities it 
is prepared for use in pharmac3 r , from pure fats or oils, 
especially linseed. Formerly, practically all the soap used 
by those living in the country was home-made. The ashes 
obtained during the winter months were put into hoppers 
and kept dry. In the spring lime was added and the mix- 
ture leached with water, added in small quantities at a 
time. These reactions took place, 

CaO + H 2 -> Ca(HO) 2 , 

Ca(HO) 2 + K 2 C0 3 -* CaC0 3 + 2KHO. 

The water, which slowly trickled from the hopper, con- 
tained the potassium hydroxide and was called lye. It 
was then boiled in large iron kettles with any waste fats 
that had accumulated during the winter. If hard soap 
was desired, when saponification was complete, salt was 
added and the whole allowed to cool. The soap floated 
on the spent lye and when cold could be lifted off and cut 



THE ALKALI METALS 319 

into cakes. Made thus it is always brown in color and 
usually contains more or less free alkali. Since soap is 
a salt made by the union of a strong base and a weak acid, 
in water owing to hydrolysis, it will give an alkaline 
reaction even if there be no free alkali contained. To 
determine whether the sample be devoid of free alkali, 
some of it must be dissolved in alcohol which does not 
cause hydrolysis. A strong alkaline test in such a solu- 
tion indicates free alkali in the soap. Floating soaps are 
produced partly by forcing minute bubbles of air into 
the soap before it is made into cakes and partly by the 
removal of much of the water present. They are more 
durable than soaps containing much water, although 
possibly a little slower in producing a "suds" or lather. 
Transparent, glycerine soaps are made by dissolving 
ordinary soap in alcohol and filtering out the insoluble 
residue; the alcohol is recovered by distillation. Such 
soaps are expensive because of the added labor in prepar- 
ing them and also from the fact that they dissolve rapidly 
in water and hence do not last well. Many soaps contain 
fillers, that is substances like sodium carbonate or water 
glass worked in by ' ' crutchers. " These consist of a 
large endless screw like an augur fitting somewhat loosely 
within a large upright cylinder. The warm, pasty soap 
is run into these, the filler added and the screw started. 
In the course of several hours the whole is thoroughly 
mixed. Some of these fillers, especially sodium carbonate, 
are not particularly objectionable, but the value of the 
water glass is doubtful. All of them cheapen the cost 
of the soap to the manufacturer. From the crutchers 
the soap is run into large molds holding several hundred 
pounds, where it hardens. It is removed from these, al- 
lowed to dry several weeks, is then cut into bars, pressed 



320 APPLIED CHEMISTRY 

into cakes by machinery, wrapped and packed almost en- 
tirely without the touch of a human hand. 

17. Sodium Nitrate, NaN0 3 . — This compound is known 
commercially as Chile saltpeter, and has been mentioned 
elsewhere. It is a white, crystalline solid, used for the 
manufacture of gunpowder, nitric acid and extensively 
as a fertilizer. 

18. Borax. — Chemically, borax is sodium tetraborate, 
Na 2 B 4 r . 10H 2 O. Our supply is obtained principally 
from the deposits of calcium borate in California. This 
natural compound is treated with sodium carbonate with 
the following reaction, 

CaB 4 7 + Na 2 C0 3 -> CaC0 3 + Xa 2 B 4 7 . 

The mixture is treated with hot water which dissolves 
out the borax, but not the calcium carbonate. AVhen 
crystallizing the salt takes up ten molecules of water. 
It is a white solid, somewhat efflorescent, giving an alka- 
line reaction in water due to partial hydrolysis. It is 
used in many washing powders, but is more expensive 
than sal soda. Small quantities are used in the chemi- 
cal laboratory in testing for various metals. When fused 
in a loop on the end of a platinum wire, it loses its 
water of combination and forms a perfectly transparent 
glass ; now, if this is dipped into a solution of certain met- 
als and again fused, or if a minute portion of certain ox- 
ides be fused with it, it forms beautifully colored " beads" 
which are distinctive. For example, cobalt gives a deep 
blue ; nickel a brown ; chromium a bright emerald green ; 
manganese, amethyst. It is commonly used in hard 
soldering as a flux. There is always a film of oxide more 
or less thin upon the surface of nearly every metal. If 
solder is poured upon such a surface it will not adhere 
because it does not reallv come in contact with the 



THE ALKALI METALS 321 

metal. When borax is applied, it melts, at the tem- 
perature necessary for doing the work, dissolves the thin 
film of oxide, and leaves a perfectly clean metal to 
which the solder strongly adheres. 

19. Occurrence of Potassium. — The third member of 
the sodium group in point of density is potassium with 
an atomic weight of 39. It is found in several natural 
compounds, but much less abundantly than sodium. 
The most common is potassium chloride, mixed usually 
with magnesium chloride. Most salt lakes contain small 
quantities of both potassium and magnesium chloride. 
The presence of magnesium chloride in table salt has 
already been mentioned. As these two chlorides are 
much more soluble in water than common salt, they 
will remain in solution until most of the sodium chloride 
has already crystallized out, Thus, in the famous Stass- 
furt deposits of Germany, the lower portions, many 
hundreds of feet in thickness, are common salt, while 
the upper layers contain much potassium and magne- 
sium chloride. Probably the same will be found true 
when the Great Salt Lake in Utah and other similar 
lakes in this country have finally become dry. At pres- 
ent, the portion separating out is largely sodium chlo- 
ride, while the water still contains the greater part of the 
magnesium and potassium compounds. Potassium ni- 
trate is also found in nature, but not in such quantities 
as the sodium nitrate beds of Chile. 

20. Preparation of Potassium. — Potassium was first 
prepared by Davy by the same method he used for 
making sodium, and in the same year. Later, for many 
years the commercial supply was obtained by heating 
potassium hydroxide with carbon. Now, however, it 
is made electrolyticall}^ by a process similar to that 
of sodium. 



322 APPLIED CHEMISTRY 

21. Characteristics of. — Potassium is a silvery-white 
metal, lighter than water, with a melting point of about 
63. Small quantities of the metal volatilized in the 
Bunsen flame give a violet color. This generally serves 
as the test for potassium salts, just as the yellow flame 
does for sodium. The vapor of potassium is green in 
color. The density of the vapor shows that it is monat- 
omic. It reacts vigorously with water even if cold, 
with the evolution of sufficient heat to ignite the hydro- 
gen set free. Sufficient of the metal is always at the 
same time volatilized to color the flame decidedly vio- 
let. The following equation shows the reaction, 

2K + 2H 2 -> H 2 + 2KHO. 

Exposed to the air reactions similar to those in the 
case of the sodium occur with the ultimate formation of 
potassium carbonate. It must, therefore, like sodium, 
be preserved in some oil like naphtha which contains no 
oxygen. Outside the chemical laboratory potassium has 
little use. 

22. Potassium Carbonate, K 2 CO ?> . — Years ago consid- 
erable quantities of this salt were obtained from wood 
ashes. Prom their treatment in large iron pots, the 
salt extracted by the water came to be known as pot- 
ashes, and later as potash, from which the name of the 
metal was derived. Since the disappearance of many 
of the original great forests, this source has become neg- 
ligible. At the present time, sugar beets furnish a very 
considerable amount. The sap is boiled down in vacuum 
pans to the point at which the crystallizable sugar will 
separate out ; the portion which will not crystallize is 
known as molasses and is separated from the sugar by 
centrifugal machines. The molasses is fermented with 
yeast and made into alcohol. From the residue the potas- 



THE ALKALI METALS 323 

shim carbonate is obtained. Another source of consider- 
able potassium carbonate is the wool of sheep. An oily 
substance called suint which sometimes equals the weight 
of the clean wool itself is secreted by the glands of the 
skin. This is removed from the wool by hot water ; from 
it potassium carbonate and a valuable oil are obtained. 
Some potassium carbonate is also prepared from potassium 
chloride, as sodium carbonate is made from the chloride. 
Potassium carbonate is a white crystalline salt, which is 
very deliquescent. Commercially, it is known as pearl 
ash. As already stated, it is used in making Bohemian 
and flint glass. From it also potassium hydroxide is pre- 
pared. 

23. Potassium Hydroxide, KHO. — This is made by 
processes exactly similar to those for making sodium 
hydroxide, thus, 

K 2 C0 3 + Ca(HO) 2 -> 2KHO + CaC0 3 . 

The calcium carbonate is an insoluble compound and the 
hydroxide may be decanted or filtered off. It may also 
be prepared electrolytically from potassium chloride as 
is caustic soda. Commercially it is known as caustic 
potash. It is a white solid, extremely deliquescent, and 
caustic, similar in all respects to caustic soda. It is used 
chiefly in making soft soap ; a special variety prepared 
for the drug trade is made by combining the caustic 
potash with linseed oil. This is used in making certain 
salves and other pharmaceutic preparations. 

24. Potassium Nitrate, KNO s . — This compound occurs 
in limited quantities in the soil in certain parts of Per- 
sia and India. It is supposed to be formed through the 
action of bacteria upon animal refuse. Considerable 
amounts are made from Chile saltpeter by treating that 
salt with potassium chloride. Potassium nitrate is a 



324 APPLIED CHEMISTRY 

white crystalline salt, not greatly different from com- 
mon salt in taste. Commercially, it is known as salt- 
peter. It is used to some extent in curing meats 
but mainly for making gunpowder. The composition is 
not materially different from that given when sodium 
nitrate is used, 75 per cent of the mixture being saltpeter. 
Sulphur and charcoal with a little moisture make up the 
balance. When exploded, the gases formed are mostly 
nitrogen and one or both of the oxides of carbon. The 
smoke produced when fired in a gun is a mixture of two or 
more solid compounds, mainly potassium sulphide and 
potassium carbonate. Partly because of the smoke and 
partly because less powerful, ordinary black powder is 
being largely supplanted by smokeless powders which 
have been mentioned on p. 156. 

25. Potassium Chlorate, KC10 3 . — This salt is a white 
crystalline solid. It melts easily in the Bunsen burner 
and decomposes, forming potassium chloride. All the 
oxygen is evolved, thus, 

2KC10 3 -> 2KC1 + 30 2 . 

In the presence of manganese dioxide, Avhich serves as 
a catalytic agent, when heated the decomposition is 
rapid. Potassium chlorate is used in the preparation of 
oxygen, in making fireworks, and in matches, as already 
described. It has a mild, cooling taste, and is sometimes 
used to allay irritation of the throat and coughing. 

26. Other Compounds. — Potassium bromide and iodide 
are white compounds which crystallize in cubes consid- 
erably larger than those of common salt, They are both 
very soluble in water, and are both used to some extent 
in medicine. The former is a sedative and the latter 
an alterative. Potassium bromide is also used in pho- 
tography as a means of preparing the silver bromide 



THE ALKALI METALS 325 

upon the plates and films. Potassium cyanide, KCN, 
is a white compound, very deliquescent, with a peculiar, 
unpleasant odor. It is one of the most violent poisons 
known. Its chief use is in silver and gold plating and 
as a means of extracting gold from its ores by what is 
known as the cyanide process. 

Exercises for Review 

1. Name tlie metals of the sodium group. By what other name 
are they known? Why s:> called? 

2. Give in some detail the occurrence of common salt upon the 
earth. 

3. Who discovered sodium? How is it prepared now? 

4. Describe sodium. How is it preserved? Why? 

5. What is an amalgam? What use is made of sodium amalgam? 

6. Give methods of preparing common salt for the market. 

7. Give the chief properties of common salt. 

8. What causes table salt to become damp? How is this pre- 
vented in some samples? 

9. Give uses for common salt. State amount used per capita. 

10. What is sodium bicarbonate? How did it receive the name? 
How is it prepared now? 

11. How is sodium carbonate made? Give steps in the Leblanc 
process and write the equations, omitting the coke from your last 
equation. 

12. Give some important uses for sodium carbonate. 

13. What is sal soda? Why does it give an alkaline reaction in 
water ? 

14. What is hydrolysis? State what kind of a litmus reaction a 
solution of each of the following will give: sodium nitrate, potas- 
sium sulphate, copper chloride, potassium carbonate, aluminum sul- 
phate, potassium chloride, ammonium nitrate. 

15. Describe the reason for each case of the above. 

16. Describe caustic soda and give uses. 

17. How is soap made? What by-product is obtained? How is 
it separated? 

18. How can you determine whether a soap contains free alkali ? 
Why will all soaps dissolved in water give an alkali test? 



326 APPLIED CHEMISTRY 

19. Give the chemical names for borax, caustic soda, Chili salt- 
peter, pearl ash, baking soda, sal soda, caustic potash, saltpeter. 

20. Give some uses for borax. Explain what it does as a flux in 
soldering. 

21. Describe potassium and compare with sodium. 

22. What is the origin of the word potassium? Give three 
sources of potassium carbonate. What uses has it? 

23. AVhat is saltpeter used for? What is produced when gun- 
powder is exploded? 

24. Why are smokeless powders supplanting ordinary black 
powder? 

25. Describe potassium chlorate and give uses. What is its pur- 
pose in a match head? 

26. What use has potassium cyanide? 

27. Give formulas for sal soda, anhydrous sodium carbonate, po- 
tassium chlorate, borax, caustic soda, pearl ash. 

28. Complete the following equations and state what they indi- 
cate: 

Na 2 C0 3 + Ca(HO) 2 -» , 
KC10 3 heated -^ , 
Na + H 2 -» , 
H 2 S0 4 + NaCa -> , 
NaHC0 3 (heated) -> , 
K 2 C0 3 + H,0 -^ . 

Note.— In completing these equations, the student may use any 
quantity needed. 



CHAPTER XXVI 

SOME LEAVENING AGENTS 

Outline — 

Chemical Agents 

(a) Baking Soda 

(&) Baking Powders 

(c) Comparative Healthful'ness 
Yeast as a Leavening Agent 
Salt-rising Bread 
Aerated Bread 
Beaten Biscuits 

1. Baking 1 Soda. — The most common chemical reagent 
used in leavening bread is sodium bicarbonate, sold 
as soda or baking soda. It has been in nse for years. 
The flour with the soda well-mixed is "wet up" with 
sour milk or buttermilk both of which contain lactic 
acid. The acid reacting with the soda, forms carbon 
dioxide as shown by the following equation, 

NaHC0 3 + HC3H5O3 -» C0 2 + H 2 + NaC 3 H 5 3 . 
The carbon dioxide, formed throughout the dough, when 
greatly expanded by the heat of the oven, tends to escape. 
In most flours there is a considerable amount of a com- 
pound called "gluten" through which the gas cannot 
readily pass : in its effort, however, the dough is raised 
and the bread is made light and porous. This gluten 
may be obtained for examination by tying a spoonful 
of flour in a thin cloth and washing for sometime in 
cold water. The starch granules will pass through the 
cloth and disappear in the water. A sticky, gummy mass, 
which is mainly gluten, will be left behind. It is a nitrog- 
enous compound and is the muscle building part of the 
flour. 

327 



328 APPLIED CHEMISTRY 

There is one difficulty in the way of successful use of 
soda as a leavening agent. It has been explained else- 
where, that it is the lactose, or milk sugar, that by fer- 
mentation produces the lactic acid in sour milk. AVhen 
the milk first begins to taste sour the quantity of acid 
present is not large, but continually increases until all 
the lactose has been changed. It is impossible to know 
without chemical test how much soda is needed to neutral- 
ize the acid present. Hence, tco little may result in a 
sour and heavy bread, or too much may produce a dis- 
colored, alkaline-tasting bread. In very warm weather 
the decomposition of milk is rapid: as it is an excellent 
medium of growth for all kinds of bacteria other prod- 
ucts besides lactic acid form, which may result in an 
unwholesome bread. 

2. Baking Powders. — The uncertainty of the results to 
be expected from the use of soda with sour milk led 
to the preparation of baking powders. There are a great 
variety of them at present, but the underlying principle 
in all of them is the same. This is the formation of 
carbon dioxide from soda by the use of an acid salt 
or its equivalent. They all. therefore, contain sodium 
bicarbonate. In addition, one class, known as the tar- 
trate powders, uses potassium acid tartrate, commercially 
called "cream of tartar." A second class, the phosphate 
powders, uses acid calcium phosphate: a third, usually 
called alum powders, uses aluminum sulphate. Besides 
these three classes there are many mixed powders, which 
usually contain mixtures of the second and third. In all 
eases starch or flour is added to the other ingredients 
to prevent chemical action taking place through exposure 
to the moisture of the air. The principle is the same as 
that employed in preventing common salt from becoming 
damp in wet weather. 



SOME LEAVENING AGENTS 329 

3. The Chemical Action. — In the tartrate powders the 
reaction is shown by the equation, 

NaHC0 3 + KHC 4 H 4 6 -> KNaC 4 H 4 6 + H 2 + C0 2 . 
It will be seen that the residue left in the baked prod- 
uct is potassium sodium tartrate, known as Rochelle 
salt. When phosphate powders are used the following 
reaction takes place, 

4NaHC0 3 + CaH 4 (P0J 2 4 CaNa 4 (P0 4 ) 2 + 4H 2 + 4C0 2 . 

As will be seen, in this case a phosphate of sodium and 
calcium is left in the bread or cake, a compound not 
greatly different from the phosphate contained in the 
bones. With the alum powders the reaction is somewhat 
more complicated. Aluminum sulphate is not an acid 
salt and its action depends upon the complete hydrolysis 
of the aluminum carbonate and the instability of the 
carbonic acid formed. This will be made clearer by 
observing the equations below, 

Al 2 (S0 4 ) 3 + 6NaHC0 3 -> 

3Na 2 S0 4 + Al 2 (C0 3 ) 3 + 3H 2 + 3C0 2 . 
This shows the results of the interaction of the two 
salts when brought together by the milk or water used 
in the dough. But it will be remembered that salts 
formed from weak acids with weak bases are completely 
hydrolyzed in water. Aluminum carbonate is such a 
compound. Hence, immediately a second reaction be- 
gins, thus, 

Al 2 (C0 3 ) 3 + 6HOH -> Al 2 (HO) 6 + 3C0 2 + 3H 2 0. 
It will be seen from the equations that the carbon di- 
oxide is evolved in two successive steps. In most of 
the alum powders, the soda is in such proportion as to 
furnish only about two-thirds as much available carl) on 
dioxide as that given by the other powders; but to offset 



ddU APPLIED CHEMISTRY 

this, the manufacturers claim that the evolution of the 
gas, in stages and not all at once, more than compen- 
sates for the smaller amount produced, in that the loss is 
much less in making up and handling the dough. It will 
be noticed that the two products which remain in the 
bread in this case are sodium sulphate and aluminum 
hydroxide. It must be remembered that baking powders 
are not used with sour milk, for the acid salt or the 
alum takes the place of the lactic acid and the different 
ingredients are so proportioned that at the close of 
the operation there shall be no excess of either. One 
or more well-known brands of baking powders incor- 
porate with the other ingredients a small quantity of egg- 
albumin. The claim of the manufacturers is that this in- 
creases the viscosity of the liquids used in making up 
the dough so that as a result the carbon dioxide will be 
retained the better. Carried out as an experiment in a 
test tube with water to bring about the reaction and 
no- flour present, this is found to be true. But in the 
biscuit, itself, the claim is a very doubtful one. Sugges- 
tions have been made to use hydrochloric acid with 
soda as a leavening agent. Its reaction is 

XaHC0 3 -HCl -> XaCl-H 2 0-C0 2 . 

It shows that only common salt is left in the bread. The 

objection to this is that the hydrochloric acid is a liquid 
and therefore cannot be mixed with the soda before- 
hand. Each separate portion would have to be meas- 
ured out at the time of using, so that the inconvenience 
might outweigh other considerations. The salt formed 
in a given quantity of bread is only about half what is 
ordinarily mixed with the flour; hence no objection 
could be offered in that respect. Scores of actual ex- 
periments with muffins, biscuits, every variety of cake 
and doughnuts, have been carried out by the author's 



SOME LEAVENING AGENTS 331 

students using soda and hydrochloric acid, with uni- 
formly successful results. 

4. Healthfulness of Baking Powders.— Owing to the 
intense rivalry among the manufacturers themselves, the 
public has taken more or less interest in the comparative 
healthfulness of the various baking powders on the 
market. A general idea prevails that the tartrate pow- 
ders are the most wholesome ; this has come through un- 
limited advertising by the manufacturers of that class 
of powders. Food experts of the United States who have 
given special attention to the effects of adulterations 
and preservatives in foods unite in saying that all bak- 
ing powders leave in the bread one or more substances 
Classed as drugs, and since no efforts have ever been made 
to ascertain the effects in small quantities of these sub- 
stances upon the human system, no one can say what the 
result is upon health. Inasmuch as the quantity con- 
sumed by any individual is not great, it is probable that 
the effects upon health are so small as to be negligible in 
the case of any of the powders. Moreover, other kinds 
of bread in which baking powders are not used seem to 
be gaining in use and popularity in America ; hence, the 
discussion may well be left until it has been settled by 
actual experiment. 

5. Yeast Bread. — A very considerable amount of the 
bread used at the present time, especially in cities, is 
what is commonly called "light bread" or that in which 
yeast is the leavening agent, Yeast is a microscopic 
plant which grows rapidly in a mixture of flour and 
water, if kept warm. As the growth proceeds, the 
sugar added and the starch which is changed into invert 
sugar as explained elsewhere, p. 220, are transformed 
into alcohol and carbon dioxide thus, 

C 6 H 12 6 -» 2aiI 5 OH + 2CO,. 



r>dZ APPLIED CHEMISTRY 

The equation showing the inversion of the starch is 

C 6 H 10 O 5 + H 2 O^C 6 H i2 O 6 . 

When the dough has risen to a certain extent it is 
kneaded back; this breaks up the bubbles of gas into 
a very large number of small ones and gives a loaf 
of much more uniform texture. When heated in the 
oven the alcohol is expelled, since its boiling point is 
only 78°. The carbon dioxide is expanded so as to 
raise the dough and the yeast plants are killed. From 
the fact that large bakeries can control and maintain 
uniform conditions of temperature in their establish- 
ments, and more than this, can secure uniform quality of 
flour by blending if necessary, their product is fast 
supplanting that made in the home. It has been said 
before that it is the gluten that serves to hold the gas 
in the dough until the baking is completed. Naturally, 
therefore, a flour deficient in this respect will not rise 
well; one with too much will produce bread too light, 
with large pores. For this reason, up to within recent 
years, it Avas difficult for the housewife with different 
flours to make a uniformly satisfactory loaf, yet with 
no fault on her part. At present, all large flour mills 
have the wheat they intend buying tested as to per- 
centage of gluten as well as in other respects. The 
flours they make are likewise tested. Thus with the 
composition known, a flour low in gluten may be mixed 
with one having a high percentage and both will be 
made right. At the present time, the output of flour 
is much more uniform than some years ago. This has 
resulted in large baking concerns themselves putting 
out a much more uniform product than was possible 
formerly. Since carbon dioxide in yeast bread is ob- 
tained through the decomposition of the starch, it will 



SOME LEAVENING AGENTS 333 

be seen that there must be considerable loss in weight. 
In baking, including the water, which escapes, this is 
fully 15 or 20 per cent. It was estimated by Liebig, a 
German chemist, some years ago, that the alcohol pro- 
duced in this way amounted in the German empire to 
twelve million gallons annually, and that the flour thus 
passing off into the air in gaseous form was sufficient 
for the bread required by an army of 30,000 men. 

Formerly the housewife was dependent largely upon 
her own efforts for a continued supply of yeast. A 
piece of dough was saved each time and put away in 
a cool place until time for the next baking. Sometimes 
this was mixed with corn meal and dried, in which case 
it was good for several weeks or even longer. Later 
dry yeast was made an article of commerce and sold 
under the trade name of "Yeast Foam." At the present 
time "compressed yeast" which is a fresh and not a 
dried yeast has largely supplanted the dry form because 
of its very much more rapid growth when put into 
"sponge." Large bakeries use a yeast in a semi-liquid 
condition closely resembling thin batter. 

6. Salt Rising Bread. — This special variety is made by 
mixing up a sponge of corn meal, and milk with some 
salt added, and allowing it to stand for some hours. 
Thereafter the procedure is not essentially different 
from that of ordinary bread. It is supposed that a 
special variety of yeast spore which grows rapidly in 
the corn meal mixture and which finds entrance from 
the air is the cause of the leavening and of the pecu- 
liar taste as well. Some few years ago this "wild 
yeast" was isolated by a graduate student at Kansas 
University, and salt rising bread may now be made 
with as much assurance of uniform results as with or- 
dinary yeast. 



334 APPLIED CHEMISTRY 

7. Aerated Bread. — On account of the loss in weight- 
in light bread as explained above, efforts have been 
made to force carbon dioxide into the dough mechani- 
cally, without the use of any yeast at all. This is done 
by putting the materials into large cylinders and pump- 
ing in carbon dioxide until a considerable pressure is 
reached. It is then kneaded mechanically by rotating 
the cylinders. After some time the dough is forced out, 
cut into suitable sizes and baked. The gas absorbed, 
having the pressure removed and the temperature 
greatly raised, expands in accordance with both Boyle's 
and Charles' laws and makes the product porous and 
light. The bread thus obtained is sweet and wholesome, 
but lacks the "yeasty" taste; it is more inclined to be 
dry than ordinary bread and has not been received well 
by the public. 

8. Beaten Biscuits. — These were probably the original 
aerated bread. No leavening agent is used, but by con- 
tinued kneading and "beating" more or less air is 
worked into the dough, which expands upon baking. 
Such biscuits are never as light as those made from soda 
or baking powder, but they retain all the relative, 
wholesome taste of the flour, with nothing objectionable 
or questionable added. The amount of time needed to 
make them is fast causing them to be an unknown ar- 
ticle of food. 

Exercises for Review 

1. Explain the action of soda in making biscuits. Write the 
equation. 

2. What prevents a gas escaping rapidly from dough? How 
may a sample be obtained for examination? 

3. What difficulty is there in obtaining uniform results with 
soda? 

4. Name the three classes of baking powders and give compo- 
sition. What is the purpose of each ingredient in the baking 
powders ? 



SOME LEAVENING AGENTS 335 

5. What is left in the bread in the case of each baking powder? 

6. Why can biscuit made from a baking powder never show an 
alkaline reaction ? 

7. Give advantages and disadvantages of using hydrochloric acid 
with soda as a leavening agent. 

8. What may be said of the relative healthfulness of the various 
baking powders? 

9. What is yeast? How does it leaven bread? Why were light 
breads in former years of such varying quality? Wiry more uni- 
form now? 

10. What can be said of the loss in making yeast bread? 

11. What is aerated bread? How is the gas introduced into the 
dough? What advantages has it? Why has it not become popular? 

12. How are beaten biscuits made? What disadvantage regard- 
ing them? 



CHAPTER XXVII 

THE CALCIUM FAMILY 

Outline — 

Members of the Group 
Occurrence of Calcium 
Properties of Calcium 
Lime 

(a) Manufacture 

(6) Uses 
Plaster of Paris 
Cements 

(a) Natural and Portland 

(5) Concrete Work 
Chalk 

Calcium Chloride 
Strontium and Barium 

1. Metals of the Group. — The metals belonging to this 
group are calcium, strontium, barium and radium, rang- 
ing in atomic weights from 40 to 226. The first three 
react with cold water and form hydroxides, which are 
strongly alkaline although not very soluble. They are 
often called the alkaline earth metals. 

2. Occurrence of Calcium. — Rocks containing calcium 
compounds are among the most abundant of the earth's 
crust. Limestone and the semicrystalline variety, mar- 
ble, are both calcium carbonate as are also corals and 
shells. Limestone is produced by the cementing together 
of shells and similar material ground up by the action 
of the waves. Fossil remains of crinoid stems and 
brachiopods are commonly seen in ordinary limestone. 
The famous coquina rock, from which the old Spanish 
fort at St. Augustine in Florida was built, is made en- 

336 



THE CALCIUM FAMILY 337 

tirely of coarse fragments of shells, firmly cemented to- 
gether. Marble is usually more free from silica and other 
impurities than common limestone. It has been subjected 
to intense heat at some time in the earth's history such 
that it was softened and upon cooling became more or 
less crystalline in structure. Chalk beds are composed of 
the remains of the shells of microscopic animals, known 
as globigerina. In some parts of the ocean at the present 
time globigerina ooze is being deposited where chalk 
beds of a future day may be found. Calcium carbonate 
also occurs in crystals, often of considerable size, in the 
shape of flat rhombohedrons and sometimes in six-sided 
crystals, known as "dog-tooth spar." It is sometimes 
mistaken for quartz, but need not be, for its hardness 
is only three in the scale while that of quartz is seven. 
Gypsum, calcium sulphate, is also widely distributed. One 
very pure variety, known as alabastine, is often beauti- 
fully colored and is used for vases and similar wares. 
The native phosphate of calcium as well as feldspars con- 
taining calcium have been mentioned elsewhere. 

3. Description of Calcium.— It has not been many 
years since calcium became an article of commerce, but 
it was first prepared more than a century ago by Sir 
Humphrey Davy, by methods similar to those he used 
for sodium and potassium. It is now made by electro- 
lyzing melted calcium chloride, much as sodium is by 
the Castner process. It is a silvery white metal, resem- 
bling sodium, but much harder. It may be cut and 
worked much as lead may be. It reacts readily with 
water with the evolution of hydrogen; when heated it 
combines rapidly with chlorine, bromine and oxygen. 

4. Lime, CaO. — This compound is made by calcining 
limestone in kilns. The native rock is heated strongly 



338 APPLIED CHEMISTRY 

with coke or wood for several days during which the 
carbon dioxide is expelled, thus, 

CaC0 3 -» CaO + C0 2 . 

The better lime kilns are arranged so that the process 
is continuous. Limestone is fed in from above, while 
the finished product may be removed at the bottom. It 
is then shipped in barrels or loose to points where 
needed. Exposed to the air lime absorbs moisture and 
carbon dioxide and crumbles to a fine powder. Ulti- 
mately it becomes a carbonate again, so that the above 
reaction might be written 

CaC0 3 «± CaO + C0 2 . 

It reacts with water vigorously with the evolution of 
much heat. Use is made of this fact by balloonists as 
a means of securing heat at high altitudes without the 
use of fire. In case of considerable quantities of lime 
in contact with wood or other combustible material, the 
temperature reached, on the addition of water, is often 
sufficient to cause combustion. An illustration of this 
was seen at the time of the flood of the Kansas Eiver at 
Kansas City in 1903, when many box cars loaded with 
lime were partially submerged in the freight yards. 
All of them took fire and burned to the surface of the 
water. 

5. Uses of Lime. — One of the most important uses is 
for making mortar in building — foundations for houses, 
brick work, stone walls, and the like. For large build- 
ings, cement is used because of its greater strength, but 
it will be seen later that cement contains a considerable 
percentage of lime. ]\Iortar is made by mixing sand 
with slaked lime. When exposed to the air, as in the 
foundation of a building, chemical reaction with the 
carbon dioxide of the air takes place, the water is evap- 



THE CALCIUM FAMILY 839 

orated, and ultimately, if properly made, the mortar 
becomes a silicious limestone. Thus, 

Ca(HO) 2 + C0 2 -> CaC0 3 + H 2 0. 

As the carbon dioxide in the air is limited in amount, 
the action is slow and probably continues for months or 
even longer. Moisture aids in the absorption. Slaked 
lime is often used to remove the hair from hides ; boiled 
with sulphur it is used as a spray to prevent fungous 
destruction of peaches, plums, grapes and possibly other 
fruits. Molded into round sticks it is used in the cal- 
cium light, already mentioned on p. 68. It is also 
valuable as a whitewash for basements, board walls, 
trees and as a cheap disinfectant. Dilute solutions of 
the hydroxide are called lime water and are used in. 
various ways in medicine. Milk of lime, which is water 
containing considerable calcium hydroxide in suspen- 
sion is used with alum in settling the mud from river 
water for city supplies, also as a means of softening 
water, which will be explained later. 

6. Plaster of Paris.— By calcining gypsum at such a 
temperature as to remove a portion of the water of 
combination, plaster of Paris is obtained. The reaction 
is 

CaS0 4 .2H 2 -» CaS0 4 .H 2 + H 2 0. 

As put on the market it is a white powder. Its most re- 
markable property is that of being able to take up water 
and change back rapidly into the hydrated form 
again. This property is called "setting." If the quan- 
tity of water is not too great it takes place in a very 
short space of time. Examination with a magnifying 
glass shows the formation of a crystalline structure. 
In preparing plaster of Paris, if the calcining is con- 
tinued sufficiently long to expel all the combined water, 
the product is called "burnt plaster'' and has very little 



340 APPLIED CHEMISTRY 

value, for it takes up water again very slowly. Plaster 
of Paris is used in the finishing coat in plastering houses, 
for making plaster casts and statuary, in dental and 
other surgery, for interior raised decorations in large 
halls, panel work, as a filler for paper pulp, for school 
crayons, and in numerous other ways. When used in 
statuarj^, to prevent injury in washing, since calcium sul- 
phate is somewhat soluble in water, the surface is 
usually treated with a solution of paraffin in naphtha or 
some similar volatile oil. Gypsum is often called "land 
plaster" and is frequently used as a corrective of alka- 
linity in soils. 

7. Cements. — This class of complex substances may be 
divided into natural and portlancl cements. They all 
contain more or less lime, usually some magnesia, MgO, 
with silica, and aluminum oxide as the main ingredients. 
The first two of these are usually found together in 
what is called magnesium limestone; the others are ob- 
tained from shale, a hydrated aluminum silicate. When a 
quarry of rock contains all of these in such proportions 
as are more or less suited for the manufacture, the cement 
made therefrom is called a natural cement. However 
when the limestone is obtained from one quarry and the 
other rock from another, it is called a portland cement. 
This last name was given in England for the reason that 
when used the finished product resembled closely a spe- 
cial building stone known as Portland rock. Natural ce- 
ments, as a rule, are comparatively high in the lime con- 
tent. As this sets by the absorption of carbon dioxide 
from the air, such cements harden slowly. In preparing 
Portland cement the separate portions are weighed in 
such amounts as have been found by experience to be 
best, are then calcined, mixed and ground to a fine pow- 
der. In the calcining two changes take place : the carbon 



THE CALCIUM FAMILY 341 

dioxide is expelled from the limestone and a part of the 
water from the hydrated shale. These steps, in a sim- 
ple way, may be illustrated thus, 

CaMg(C0 8 ) 2 -> CaO + MgO + 2C0 2 , 

Al 4 (SiOJ 3 nH 2 -> Al 4 (Si0 4 ) 3 mH 2 + xH 2 0. 

As plaster of Paris sets quickly through the hydration of 
the molecules, so any cement with the partially dehy- 
drated silicate in excess will also. Since this is true of 
all portland cements, they harden rapidly even in the 
presence of much moisture and are for this reason often 
called hydraulic cements. For work in very cold weather 
cements with very high content of silicate are sometimes 
used ; hence, they set before they have time to freeze. 
On the other hand, natural cements cannot be used under 
any such conditions or where much moisture will be pres- 
ent, as in piers for bridges, sewers, and similar places, 
for they set too slowly. Likewise, they cannot be used in 
large buildings, for the weight to which they are subjected 
before thoroughly hardened is sufficient to crush them. 

Concrete is made by mixing cement, sand and crushed 
rock, often called "grits," in the proportion of 1, 3, and 5. 
Water is added and the whole rotated in a mechanical 
mixer till relatively homogeneous. This is then poured 
into position and allowed to harden. Thus are made 
roadways, sidewalks, foundations, bridge piers, and a 
vast number of other things. Much of the building in 
cities now is of reenforced concrete. This is made by 
putting iron rods into position and pouring the concrete 
mixture over and about them. For roadways, woven wire 
fencing is sometimes used. Floors of fireproof buildings 
and roofs, supported temporarily by false woodwork are 
thus made. The reenforcement enables the concrete to 
withstand any sudden shocks or great strain. The great 



o4Z APPLIED CHEMISTRY 

earthquake and fire resulting in San Francisco in the 
spring of 1906 gave great impetus to this method of build- 
ing. It was found that the reenforced, fireproof con- 
struction was able to stand with relatively little damage 
even such terrible forces of destruction. During the last 
year of the Great "War reenforced concrete was even used 
for a number of medium-sized ocean going vessels. Its 
uses are being extended more and more every year, since 
lumber is becoming more scarce. In 1915, government 
bulletins showed that there was an output in the United 
States of 90,000,000 barrels of cement, with great in- 
creases each year over the preceding. During the war 
this fell off some, because little building was done, but 
only temporarily. 

8. Prepared Chalk. — Native chalk, it has been said, is 
formed from the minute shells of sea animals cemented 
together. It may be prepared artificially by treating 
a solution of some calcium compound with sodium car- 
bonate in solution, thus, 

CaCl 2 + Na 2 C0 3 -» CaC0 3 + 2NaCl. 

The carbonate is a white precipitate; it is filtered out, 
washed, and molded into the desired shape or used as a 
powder. Properly made it is a perfectly smooth powder, 
entirely free from any gritty feeling. It is used in 
tooth powders and pastes, as well as in a variety of 
other Avays in pharmacy. 

9. Calcium Chloride, CaCL. — This compound is a 
white solid obtained as a by-product in the Solvay proc- 
ess of making sodium carbonate and in some other 
manufactures. For example, 

2XH 4 Cl + CaO -> 2XH 3 + H 2 + CaCl 2 . 

By evaporation of the solution thus obtained, the salt 
crystallizes out as a clecahydrate, CaCl 2 + 10H 2 O, which 



THE CALCIUM FAMILY 343 

is very soluble in water and hence very deliquescent. 
If heated strongly the hydrate loses all its water and 
becomes a dry, porous solid. It is this form which is 
most desirable for drying gases in the laboratory. A few 
cannot be dried this way, as they form molecular com- 
pounds resembling hydrates. For example, ammonia 
unites with the calcium chloride, eight molecules for 
one and forms a compound with the formula, CaCl 2 + 
8NH3. The crystalline variety is used in the brine 
tanks of many refrigerating plants instead of common 
salt. It is said to attack the metal pipes and boxes less 
than the sodium chloride does. Since a solution of cal- 
cium chloride may be made that will not freeze except 
at very low temperatures it has the advantage of being 
able to be transmitted considerable distances in re- 
frigeration systems and still possess such a degree of 
cold as may be necessary. Since the supply of calcium 
chloride is greater than the demand, attempts have 
been made to find other uses for it. For preventing 
dust on roadways its use has been mentioned on p. 143. 
In many localities asphaltic petroleum is used. This 
prevents erosion by heavy rains, as well as by winds and 
heavy traffic. The calcium chloride cannot prevent dam- 
age by rains on account of its great solubility. 

10. Other Members of the Group. — Strontium and ba- 
rium occur in native compounds corresponding to those 
of calcium, the sulphate and carbonate. Barium sul- 
phate, especially that made artificially, is used in many 
ways for adding weight. Paper pulp intended for card- 
board and white paints often contain it as a filler, or 
adulterant. 

The nitrates are both used in making fireworks and 
colored fires. Fusees, used upon railways to give warn- 
ing of the nearness of another train, contain mixtures of 
strontium nitrate, shellac or sulphur and potassium ehlo- 



344 APPLIED CHEMISTRY 

rate. The strontium compound gives the red color, the 
chlorate furnishes oxygen for rapid combustion, and the 
remaining portion is the fuel. Barium nitrate used in the 
same way gives a green fire. These were formerly used 
extensively for stage effects and still are where the 
electric spot light is not available. If to be burned 
indoors, shellac and not sulphur should be used on ac- 
count of the fumes produced. 

Strontium hydroxide. Sr(HO) 2 , is used in the refining 
of cane sugar. It causes the separation of portions of 
sugar from the molasses after the main crystallization 
has taken place which would not otherwise be obtained. 
Barium forms both a monoxide. BaO. and a dioxide. 
Ba0 2 . The latter is of interest in that it may be used 
for the manufacture of hydrogen peroxide, thus. 

Ba0 2 + H 2 S0 4 -> BaS0 4 -H 2 2 . 

Barium hydroxide, Ba(HO) 2 . is often used in the labora- 
tory as a reagent instead of lime water. 

Exercises for Review 

1. Xarne the metals of the calcium group. By what other name 
are they known? 

2. Give some of the familiar natural compounds of calcium. 
What is coquina? Marble? Chalk? Alabastine? 

3. How may calcite be distinguished from quartz when the crys- 
tals resemble? 

4. How is calciiun prepared? Describe the metal. 

5. How is lime made? Equation? 

6. Give the characteristics of lime. 

7. Give important uses of lime. How does mortar harden? 
Show by an equation. 

8. How is plaster of Paris made? What is its most remarkable 
property ? 

9. Give uses of plaster of Paris. What is land plaster? 

10. Xame the two classes of cements and state how each is 
obtained. 



THE CALCIUM FAMILY 345 

11. What advantage has portland over the other? Can you 
think of any reason why the natural might be preferred? 

12. What is concrete? How does it harden? What is reenforced 
concrete? 

13. How is prepared chalk made? Give uses. 

14. What is the source of the calcium chloride of commerce? 
What two varieties? Explain the difference between them. 

15. Give some valuable uses for calcium chloride. 

16. Give some uses for the nitrates of strontium and barium. 
Why are they so used? 

17. Name some other compounds of barium and strontium that 
are of some use. 

18. Complete these equations, using amounts needed, 

Ca(NO s ) 2 + Na 2 C0 3 -> •, 
Ba(HO), + HCl -* , 
SrC0 3 + HN0 3 -* , 
Sr(N0 3 ) 2 + NH 4 HO -^ . 



CHAPTER XXVIII 

HARD WATERS— METHODS OF SOFTENING 

Outline — 

Kinds of Hard Waters 
Effects of Hard Waters 
Treatment for Hardness 

(a) In the Home 

(6) For Commercial Enterprises 
Effects of Coagulants upon City Supplies 
Hardness as Related to Soap 
Method of Estimating Hardness 

1. Kinds of Hardness. — Any water containing mineral 
matter in solution which will cause a precipitate with 
a soap solution is said to be hard. The soap solution 
must be perfectly clear: when added, the formation even 
of a slight cloudy appearance shows that the water is 
distinctly hard. More often hardness is caused by the 
presence of calcium or magnesium salts, but occasionally 
by iron. When the hardness is such that boiling will re- 
move it, it is said to be temporary ; otherwise it is perma- 
nent hardness. This does not mean, however, that there 
is no possible way of removing it. Both kinds of hardness 
may be present and often are. Temporary hardness is 
caused by the presence in the water of the acid carbonate 
of calcium or magnesium, often called the bicarbonate, 
CaH 2 (C0 3 ) 2 . When boiled, decomposition takes place, 
with the formation of the normal carbonate. This being 
insoluble in water precipitates out, thus, 

CaC0 3 .H 2 C0 3 -> CaC0 3 -f C0 2 + H 2 0. 

It is the compound, CaC0 3 , which collects upon the inside 
of teakettles as a rough deposit, also in the hot water coils 

346 



HARD WATERS METHODS OF SOFTENING 347 

in furnaces and water heaters, and in all steam boilers 
which use hard water. It is one of the greatest annoy- 
ances with which the engineer has to deal as well as one 
of great expense. All sorts of "water softeners" have 
been put upon the market under various names, many 
of them worthless. Fig. 62 shows two actual cases of 
sections of pipe taken from two manufacturing plants, 
which show that the "boiler scale" as it is called had 
nearly closed the pipes. It is said that a layer 14 i ncn i D 
thickness lessens the heating effect by half, or in other 




Fig. 62. — Scale in iron pipes, from an actual case. 

words it is the equivalent of an iron pipe 5 inches in 
thickness. In the cases shown in Fig. 62 the scale was 
about % inch thick. Under such conditions, in gas heaters 
or furnace coils, in the home, the water in the tank is 
warmed very slowly, while the iron of the pipe is being 
rather rapidly burned away. Finally, it becomes so thin 
that under the water pressure it bursts, and must be 
renewed. 

Permanent hardness is caused usually by the presence 
of sulphates of calcium or magnesium, although the chlo- 
ride, especially of magnesium, may be the cause. As these 



348 APPLIED CHEMISTRY 

compounds are not decomposed at the temperature of 
boiling water, they remain in solution. 

2. Removal of Temporary Hardness.— Since temporary 
hardness is caused by the presence of an acid salt, it 
would seem that naturally an alkali would remove it. 
For laundry and bath purposes at home, dilute ammonia 
water is thus often employed. The reaction is shown by 
the equation, 

CaC0 3 .H 2 C0 3 + 2NH 4 HO -» CaC0 3 + (NHJ 2 C0 3 . 

As the calcium carbonate is not soluble in water it set- 
tles to the bottom and leaves the water soft. The am- 
monium carbonate, unless present in large quantities 
has little effect upon the soap, hence is not objection- 
able. If much water is to be treated, this method is too 
expensive. Therefore, steam laundries, many of which 
use from 50,000 to 100,000 gallons of water per day, and 
other similar establishments, must employ a cheaper 
alkali. The cheapest known is lime water, and this is 
used. Daily analysis of the water is made so as to 
know exactly the amount of hardness present. This be- 
ing known, into large settling tanks, holding sufficient 
for a day's run, milk of lime is added sufficient to com- 
bine with the acid carbonate and convert it into the 
normal salt. This reaction takes place, 

CaC0 3 .H 2 C0 3 + Ca(HO) 2 -> 2CaC0 3 + 2H 2 0. 

The precipitated carbonate settles to the bottom and is 
then drawn off to the sewers. Lime water cannot be 
employed in the home because the quantity of water 
used is relatively small and any excess of the reagent 
would leave the water as bad or worse than before. 
Many cities, with river water more or less muddy, use 
milk of lime as already mentioned on p. 45 in removing 
the turbidity. Not only does it accomplish this, but to 



HARD WATERS — METHODS OF SOFTENING 349 

prevent any excess, even minute, of the alum or whatever 
is employed as a coagulant, a very slight excess of lime 
is used. This reacts, as shown above, with the precipi- 
tation at least of a portion of the temporary hardness. 
In such treatment of water, however, for turbidity, the 
permanent hardness is always increased as the equation 
will show, 

Al 2 (S0 4 ) 3 + 3Ca(HO) 2 -> 3CaS0 4 + Al 2 (HO) 6 . 

The aluminum hydroxide is the gelatinous coagulum 
which drags down the mud, but the calcium sulphate is 
soluble to a degree and in this way adds to the perma- 
nent hardness as stated. 

3. Removal of Permanent Hardness. — For removal of 
this in large plants the water is treated with the requi- 
site amount of sodium carbonate in solution. This reac- 
tion then takes place, 

CaS0 4 + Na 2 C0 3 -> CaC0 3 + Na 2 S0 4 . 

The sodium carbonate is added at the same time as the 
milk of lime previously mentioned. The precipitate, it 
will be noticed, is the same as in the other case; both 
will settle together and be removed at the same time. 
Sodium sulphate in this case remains in the water, but 
in small quantities causes no appreciably bad results. 
In large amounts any sodium salt would cause the pre- 
cipitation of the soap when added, from ionic reasons. 
This was found true when hydrogen chloride was passed 
into a solution of common salt to produce pure sodium 
chloride. (See p. 309.) 

The Permutit System. — This is sometimes called the 
zeolite process, and is protected by rigid patents. The 
water containing the calcium or magnesium compounds 
is made to flow through cylinders containing an artificial 
sodium compound known as zeolite. In the process the 



350 APPLIED CHEMISTRY , 

magnesium and calcium in the hard water are removed 
by interchange with the sodium in the zeolite. It is said 
the water is rendered perfectly soft. In the case of very 
hard waters, however, considerable amounts of sodium 
salts are introduced into the softened water. As this is 
objectionable, the water must be further treated with 
lime as described already. 

4. Effects of Hardness upon Soap. — Without the soft- 
ening of the water used in large plants, the cost of the 
soap item would be enormous. No work can be done by 
soap as long as the water is hard, for it reacts with 
the compounds of calcium present thus, 

CaS0 4 + 2NaC 17 H 35 COO -> Na 2 S0 4 + Ca(C 17 H 35 COO) 2 . 
The equation shows by the interaction that a calcium 
stearate is formed, a species of soap, which is insoluble 
in water, and floats. It forms the disagre3able, greasy- 
feeling scum upon such waters and adhering to the sides 
of the bath tub. In laundry work it sticks to the clothing 
and under the hot iron it melts like wax and is thus spread 
out upon the garment as a dark gray or dirty looking spot. 
So with hard water, aside from the expense, high quality 
work in a laundry is impossible. When the soap has 
combined with all the calcium salts present in the water 
then it can begin to form emulsions for the removal of 
the foreign matter from the clothing, but not before. In 
all cities using hard water the soap bill is a constant 
tax upon the people. In Glasgow, Scotland, a few years 
ago, a change was made from the hard water supply which 
had been used for years to one much softer. In the 
first year the saving in soap bills was estimated at $200,000. 
In the home, therefore, if the water is appreciably hard, 
small quantities of sal soda with very little ammonia 
water should be used both as a means of economy and for 
better results. Borax, as a water softener, when delicate 



HARD WATERS — METHODS OF SOFTENING 351 

garments are to be laundered or for washing the hair, 
is regarded as preferable to sal soda. Its reaction upon 
the hard water is not essentially different from that of 
the soda, except that the calcium is changed into a borate 
instead of a carbonate, thus, 

Na 2 B 4 7 + Ca'S0 4 -> CaB 4 7 + Na 2 S0 4 . 

5. Degree of Hardness. — Hardness in water is esti- 
mated in degrees. Thus, water which contains 1 grain, 
or about y 15 of a gram, in a gallon, of calcium carbonate 
or its equivalent of any other calcium salt is said to have 
one degree of hardness. This is about the equivalent of 
one part of calcium carbonate in 50,000 or 60,000 of 
water. For every hundred gallons of water with one de- 
gree of hardness, between 2 and 2^ ounces of soap must 
be used simply to remove the hardness before doing any 
cleansing. Not only is this much soap wasted, but the 
greasy precipitate gathers upon the clothing as men- 
tioned. For a family of four it is estimated that about 
16 pounds of soap would be required in a year to soften 
the water alone. Hardness sometimes reaches as high as 
ten or even twenty degrees in which case the soap used is 
no small item, when the laundry work is done at home. If 
treated with sodium carbonate, a little over % ounce 
is sufficient to remove one degree of hardness from 100 
gallons of water; 5 or 6 pounds would be sufficient for 
laundry and bath purposes for a whole year. With 
ten degrees of hardness 50 to 60 pounds would be needed. 
hSince a pound of sal soda is very cheap it becomes a 
matter of great economy to soften the water thus be- 
fore adding the soap. 

Exercises for Review 

1. What is meant by hard water? What two kinds are there? 
Explain the difference? 



352 APPLIED CHEMISTRY 

2. Can water be both temporarily and permanently hard? Ex- 
plain. 

3. What produces temporary hardness? Permanent? 

4. What is boiler scale? Show by an equation how it forms. 

5. How may temporary hardness be removed at home? On a 
large scale how is it done? 

6. What is the effect upon city waters of removing the mud by 
a coagulant? 

7. How do laundries soften the water for their work? Show by 
equations how they remove both kinds of hardness. 

8. What is meant by one degree of hardness? How high may 
water run? 

9. State effect of great hardness upon cost of living. 

10. What is the effect of hardness upon soap? What unpleasant 
results follow the use of soap in hard water? 

11. Complete these equations: 

CaH 2 (C0 3 ) 2 + soap — > , 
CaS0 4 (heated) ^ , 
CaS0 4 + NH 4 HO -^ , 
CaS0 4 + Ca(HO) 2 -> , 
CaH 2 (C0 3 ) 2 + NH 4 HO -> , 

In which of these five equations is the water softened and in 
which not? 



CHAPTER XXIX 

CLEANING AND POLISHING 
Outline — 

Necessity for Cleanliness 
Solutions and Emulsions 
Cleansing by Soap 

Chemistry of 
Dry Cleaning 
Sinks and Waste Pipes 
Cleaning Metal Wares 

(a) Silverware 

(6) Copper and Brass 

(c) Aluminum Vessels 

(d) Nickel 

1. Importance of Cleanliness. — The great problem of 
modern civilized life is that of cleanliness. It is the one 
great contributing factor of health. Formerly soap was 
used largely as a medicinal preparation and not as 
a detergent. Real cleanliness was almost unknown and 
impossible : epidemics swept unchecked through commu- 
nities. Perfumes were adopted as disguise for lack of 
cleanliness. 

2. Emulsions and Solutions. — If a little oil be shaken 
in a test tube with some ether, the oil disappears and 
we have a homogeneous mixture which is called a solu- 
tion. If the experiment be repeated with oil and water, 
the two may be mixed by vigorous shaking, but the oil 
soon separates out and rises to the top. Again, if some 
soap be added to the oil and water in the tube and 
shaken for some time, the oil disappears and only sepa- 
rates out again very slowly. Moreover, the resulting 
mixture has become cloudy or even milky in appearance. 

353 



354 APPLIED CHEMISTRY 

It is called an emulsion. Milk is probably the most famil- 
iar example of emulsions and the oil in the form of 
cream only slowly rises to the top. 

3. Cleansing Action of Soap. — Just what is the action 
of soap in cleansing by means of it is somewhat a matter 
of question. As a rule "dirt" or foreign matter ad- 
heres to clothing or to the body because of oily matter 
present. "Clean" mud when dry may be easily brushed 
off. but mixed with grease it cannot. If in some way the 
oil or grease may be removed, then the dirt is carried 
away mechanically by the water. But oils are not solu- 
ble in water, hence cannot be removed thus. Hot water 
may melt the grease and cause more or less of it to float 
away, but even this is imperfect. The use of soap is the 
most common method. It has been seen that in water 
soap is hydrolyzed with the formation of some sodium 
hydroxide. It is believed by some that this free alkali, 
especially if the water be warm, saponifies the oil upon 
the garment or body, and that the water then dissoh^es 
and carries it away together with the dirt. This may 
occur to some extent, but the process of saponification 
is too slow, apparently, to account for all that happens. 
What seems more probable is. that the soap forms an 
emulsion with the oil and that it is thus removed to- 
gether with the associated foreign matter. This process 
is fairly rapid. In accordance with this idea and to 
aid in the emulsifying of a solid fat there are soaps on 
the market which contain a considerable percentage of 
naphtha or some other oil. In laundry work the naphtha 
is believed to dissolve the grease on the garment and 
then the liquid emulsifies more easily with the soap. 
Very hot water is not desirable in the use of such soaps 
as they tend to evaporate the naphtha before it has dis- 
solved the grease. Upon cotton goods soaps with not 



CLEANING AND POLISHING 355 

over 1 per cent of free alkali may be used without seri- 
ous results ; for woolens and for toilet purposes there 
should be none present. For rough cleaning, as of floors, 
unfinished, free alkali in soap is not objectionable, but 
upon painted or varnished surfaces it is injurious. 

4. Dry Methods of Cleaning-. — Sometimes the nature 
of the fabric does not admit of the use of soap and wa- 
ter. In such cases, sometimes, it is possible to remove 
the grease by heat and an absorbent. Below the spot is 
placed a sheet of blotting paper or Fuller's earth, or 
French chalk, or some similar porous agent. A hot iron 
applied above will melt the grease and tend to expel it. 
Then it will be largely taken up by the absorbing agent. 
In ordinary dry cleaning a volatile solvent is used. The 
oil is dissolved out of the garment and the foreign matter 
washed away mechanically. Ether is one of the most ex- 
cellent solvents known for oils and fats, but it is too ex- 
pensive for ordinary use; moreover, it is very inflamma- 
ble. Carbon tetrachloride is also an excellent solvent for 
oils, and is not inflammable, hence perfectly safe. It is 
more expensive, however, than some other agents. Ben- 
zine and gasoline are both good solvents for oils and are 
the most commonly used on account of their cheapness. 
However, they are very inflammable, and carelessly han- 
dled are the cause of many explosions and fires. 

Painters and workmen about oily machinery ordinarily 
remove the dirt from their hands, first by some solvent. 
Kerosene or gasoline upon "waste" will dissolve the lin- 
seed oil in the paint or the grease as the case may be, and 
soap will finish the process". 

5. Ink and Other Stains. — Ordinary black ink since 
it is made from green vitriol and nutgalls may be re- 
moved by applying a solution of oxalic acid in water. 
Usually a few minutes is sufficient. The spot should 



356 APPLIED CHEMISTRY 

be washed with water afterward. Other black inks may 
generally be removed from clothing by moistening the 
spot with a solution of bleaching powder in water. Af- 
ter allowing to stand a few minutes, add vinegar and 
wash with water. Violet and other anilin inks may 
usually be removed with bleaching powder solution 
without great difficulty. But it must be remembered 
that this method cannot be used upon a colored article, 
as it will be bleached. 

From the common use of red ink in bookkeeping acci- 
dents sometimes occur. For the removal of such stains a 
mixture of about twenty parts of denatured alcohol with 
one of nitric acid is recommended. 

Iron rust may generally be removed by moistening 
with citric acid or lemon juice and exposing to bright 
sunlight. Usually one treatment is sufficient. Indelible 
inks, which usually or often contain silver nitrate, may 
be removed by a solution of ammonium chloride and cor- 
rosive sublimate — 10 grams of each in 80 c.c. of water. 
This should be rubbed on with a soft cloth. Lunar 
caustic stains upon the hands may thus be removed. 

Fresh paint upon clothing may be removed by apply- 
ing turpentine or benzine, better with a cloth or blotter 
beneath to absorb the oil. Old or dried paint on wood- 
work may be removed by applying a mixture of aqua 
ammonia and a 25 per cent solution of sodium hydrox- 
ide, one part each, with five parts of water glass. Allow 
it to remain on the wood till the paint has softened, then 
wipe off. 

Pencil marks and soiled spots upon tracing cloth may 
be wiped off with benzine upon a soft cloth, without 
affecting the ink drawing at all. Oily stains upon wall 
paper may often be removed by applying a paste of 
kaolin and water or magnesia in benzine and allowing 



CLEANING AND POLISHING 357 

to remain about twelve hours. Then rub off gently with 
a soft cloth. Sometimes a second application is neces- 
sary. 

Nitric acid stains upon the hands are very difficult of 
removal. One of the best plans is to apply a strong so- 
lution of potassium permanganate and after a few min- 
utes wash off with hydrochloric acid, about 5 per cent 
in strength. 

6. Cleaning Waste Pipes. — It often happens that waste 
pipes from kitchen sinks becomes more or less clogged 
so that water is only carried away slowly, if at all. 
This is usually largely the result of carelessness. The 
grease removed from the dishes by hot water and soap 
becomes solid again when the water is cooled in the 
trap, and adheres to the waste pipe. If coffee grounds 
or other similar solids are poured into the sink they are 
caught by the grease and in course of time fill the trap 
and waste pipes. If care is taken never to put any such 
solid material into the sink there will seldom be any 
trouble. The grease may solidify upon the pipe but 
the alkali formed by the hydrolysis of the soap and from 
the washing powders will gradually saponify it and re- 
move it. Especially will this be true if occasionally a 
spoonful or two of some washing powder be dropped 
into the strainer of the sink and allowed to stand in 
the trap over night. In very bad cases some caustic 
soda or lye dropped upon the strainer and left over 
night will generally open up the pipe so that warm wa- 
ter will clean it out, without the aid of the plumber. 

7. Cleaning Metal Surfaces. — Most metals exposed to 
the air if moisture be present become tarnished either 
through the action of the oxygen or because of some 
other gas present in the atmosphere. Upon articles 
commonly used in the home this action is relatively sIoav 



dDO APPLIED CHEMISTRY 

as a rule, so that only in the course of weeks does it 
become appreciable. In the case of silverware, the coat- 
ing is a sulphide ; usually with other metals it is some 
form of oxide. Obviously, anything which would dis- 
solve the oxide, or sulphide, would remove it and leave 
the surface as bright as before. Frequently, however, 
a reagent that will dissolve the film will also react with 
the metal itself. Hence, great care must be exercised 
in the use of such cleaning agents. In the case of sil- 
verware, the sulphide coating is readily soluble in a so- 
lution of potassium cyanide and may be quickly removed 
in that way. But since potassium cyanide is a most 
violent poison, its sale is restricted and this method is 
not suited to the home. All small silver articles, such 
as knives, forks and spoons, may be readily cleaned by 
putting them into some aluminum vessel, covering with 
water and warming for a few minutes. Some think the 
addition of a little salt is helpful. As aluminum is much 
more electropositive than the silver, the sulphur is thus 
removed from the less positive metal and it is left clean 
and bright. There are many silver polishes to be had 
on the market, but they require more work and time and 
are more harmful to the silverware. A home-made 
powder, which is good and harmless, may be made of the 
following common substances, 

Prepared chalk, 3' parts, 
Tartaric acid, 3 parts, 
Powdered alum, 1 part. 

Oxalic or citric acid may be substituted for the tartaric. 
The oxalic is usually the cheapest. Lemons contain citric 
acid. All must be finely powdered and Avell mixed 
together. The mixture is to be applied with a soft, 
damp cloth. 



CLEANING AND POLISHING 359 

8. Copper and Brass. — The film of oxide upon copper 
and brass articles is soluble in ammonium hydroxide. 
Usually, therefore, polishes made for such surfaces con- 
tain some ammonia. Venetian red, rouge, whiting, or 
any similar powder, mixed with water and a little am- 
monia work well upon these metals. It is necessary in 
using such a polish, to wipe the surface perfectly dry 
and clean at the close, for the alkali also attacks the 
metal and if left would cause it to tarnish again and 
quickly. Polished brass articles are usually protected 
by a thin coat of lacquer. This is made by dissolving 
shellac in alcohol. It is applied by means of a soft 
brush. 

9. Aluminum Ware. — Kitchen ware made of aluminum 
does not tarnish readily, and usually nothing more than 
ordinary cleanliness is needed to keep it in good shape. 
Putty powder, whiting or rouge mixed with a little 
oil are good for polishing if needed. The addition of 
some organic acid like the juice of lemon or oxalic may 
be helpful. Strong alkalies attack aluminum readily; 
hence, washing powders that contain free sodium hy- 
droxide, as many of them do, should be used only spar- 
ingly and not left to stand in the vessel. 

10. Nickel and Other Metals. — Nickel plated surfaces 
may be cleaned by polishing with whiting or rouge, 
mixed with some organic acid. Vinegar or oxalic are 
good. Iron vessels are so readily attacked by oxygen 
in moist air that they are not used unprotected. The 
various methods for preserving such surfaces are men- 
tioned elsewhere. For tin cans, tin plate is used, for 
which, see page 403. For larger articles, steel plate 
is galvanized, mentioned on p. 384. For cooking vessels 
much " granite ware" is still used. Kitchen stoves are 
protected often by enamels, baked on at intense heat. 



360 APPLIED CHEMISTRY 

These may gradually wear off, when they should be 
replaced by a prepared article to be had at hardware 
and automobile supply houses. Heating stoves are usu- 
ally protected by a thin film of magnetic oxide of iron, 
put on by treating the metal with superheated steam. 
This gives the surface a bluish color. It is sometimes 
spoken of, in the case of stove-pipe especially, as "Rus- 
sia iron. ' ' This film adheres firmly and is fairly durable. 
Such surfaces do eventually rust, however. Prepared 
polishes usually containing graphite, are applied and 
polished by rubbing briskly with a stiff brush. Liquid 
polishes are to be had which dry with a gloss and need 
no rubbing, but often they burn off at the first heating 
and are of little value. 

Exercises for Review 

1. What is an emulsion? How is it different from a solution? 
Illustrate. 

2. Name some very common emulsion. How may an emulsion of 
soap and kerosene be made? 

3. Give the cause for dirt adhering to clothing. What is the 
tlieory underlying the cleaning of clothing? 

4. Give two theories regarding the. cleansing action of soap. 

5. Which is the more plausible of these theories? Wherein lies 
the value of a soap containing naphtha? 

6. W T hy are soaps with free alkali objectionable with woolens? 
Why do they make the hands chap? 

7. Describe one method of removing a grease spot from a gar- 
ment by heat. 

8. Give the usual method of dry cleaning. What is the prin- 
ciple involved? 

9. Name the solvents that might be used in dry cleaning. What 
advantage has each? Why is benzine commonly used? 

10. What is the best means of cleaning the hands when badly 
soiled by working about machinery? 

11. What kinds of soaps should be used upon finished woodwork, 
iC any? Why do you say so? 



CLEANING AND POLISHING 361 

12. What is usually the cause of stoppage in wastepipes in 
kitchen sinks? How may they be kept clean? 

13. If already stopped, how may a waste pipe as a rule be 
opened? 

14. What is the cause usually of metals tarnishing? What in 
the case of silverware? 

15. Give some easy way of cleaning small articles of silver. 
Explain the chemical action. 

16. How is brass usually protected against tarnish? What do 
most copper and brass polishes contain? Why? 

17. Why do tomatoes, rhubarb, and similar articles of food tend 
to keep aluminum cooking vessels bright? Why should strongly 
alkaline washing powders not be used much upon aluminum ware? 

18. How may one know by the feeling in water whether a wash- 
ing powder contains much free caustic soda? 

19. Name some ways of protecting the iron used in the home. 
What is Eussia iron? How are stoves usually polished? Why is 
this substance commonly used? 



CHAPTER XXX 

THE COPPER GROUP 

Outline — 

Members of the Group 
Copper 

(a) Occurrence 
(6) Characteristics 

(c) Uses 

(d) Alloys 
Compounds 

(a) Blue Vitriol 

(6) Other Compounds 
Silver 

(a) Occurrence 
(&) Characteristics 
(c) Uses 
(tf) Compounds 

(a) Silver Nitrate 

(6) Silver Chloride 

(c) Silver Bromide 
Photography 

(a) Principles Involved 

(b) Developing 

(c) Printing 

(d) Kinds of Papers 

(e) Blue Prints 
Gold 

(a) Occurrence 

(b) Methods of Mining 

(c) Characteristics 

(d) Uses 

1. Members of the Group. — To this group belong three 
metals all of which are found free in nature. For this 
reason they have been known from most remote times. 
Moreover, all are soft metals, hence easily worked even 

362 



THE COPPER GROUP 363 

without any great advancement in scientific processes. 
They are often spoken of as the "noble metals," a term 
applied to all which may be separated from their ores 
by heat alone. In the periodic table they are found at 
the left hand in the same division as sodium and potas- 
sium. It will be noticed, however, that they are placed 
on the right side of this column and not under the alka- 
li metals. In the study of the table it was said that the 
metals seemed to arrange themselves in octaves and 
that those with the same properties occur at intervals 
of eight. It should be added here that after Ave pass 
potassium, these periods become double octaves ; that is, 
leaving potassium, a single octave brings us to copper 
which is so different from the alkali metals that it was 
placed at the right of the space as a member of another 
family; again proceeding, another octave brings us to 
an alkali metal which is placed under sodium. In this 
way, copper, silver and gold are at the center, as it were, 
of three long periods or double octaves, and are classed 
together. In many ways they are alike ; in other respects, 
they are dissimilar ; but in nearly all their properties they 
are utterly unlike the alkali metals. Silver has a valence 
of one ; copper is usually regarded as bivalent, although 
it forms unsaturated compounds where it appears as if 
univalent. Gold is trivalent, but forms one or more com- 
pounds in which it appears as if univalent. They are all 
malleable, ductile, and good conductors of electricity. 

2. Occurrence of Copper. — By the Greeks and ancient 
Phoenicians copper was obtained from the mines upon 
the island of Cyprus. This gave the metal its name, Jx up- 
rum, from which it derived the sjanbol. In America the 
longest known deposits are those of the Lake Superior 
and Michigan regions. From copper vessels found in the 
mounds of prehistoric tribes it is known that they were 



364 APPLIED CHEMISTRY 

familiar with these deposits. The outcropping metal was 
in thin sheets between layers of rock. By cracking this 
off, sometimes by heavy stones, sometimes apparently by 
fire, the thin sheets were obtained and beaten into rude 
vessels. These deposits are still valuable and some of the 
mines as the Calumet and Hecla, though at a depth of a 
mile or more, are still heavy producers. The copper in 
this region is mostly pure and is separated from the rock 
mechanically. 

Western Deposits. — In several of the western states, es- 
pecially Montana, Colorado, Arizona and New Mexico, 
copper occurs mostly in the form of compounds of great 
variety. Many of them are sulphides having different 
content of sulphur, and known under a variety of names. 
Such are bornite, copper glance, peacock ore, and calcho- 
pyrite. Two basic carbonates, called azurite, deep blue 
in color, and malachite, a deep green, are known. 

3. Characteristics of Copper. — Copper is a red metal 
with a specific gravity of about 11, and melts at a tem- 
perature of about 1,090° C. It tarnishes somewhat in 
damp air, but since the film of oxide adheres firmly to 
the metal the oxidation is merely superficial. In the 
presence of much moisture carbon dioxide is also taken 
up from the air forming a greenish compound of basic 
copper carbonate. It is a very tenacious metal, mallea- 
ble and ductile. Wires may be made of a diameter but 
little greater than 1/1000 of an inch of which a length 
measuring a half mile would only weigh about 5 grams. 
It does not decompose either sulphuric or hydrochloric 
acids in the cold, for the reason that it is well down the 
electromotive series of metals as shown on p. 65. It 
does decompose nitric acid rapidly, because of it's ready 
union with oxygen. It is an excellent conductor both 
of heat and electricity. 



THE COPPER GROUP 365 

4. Uses of Copper. — Copper has many and varied uses. 
Because of the fact that it tarnishes only on the surface 
it is valuable for cornice work, roofing and guttering 
and is frequently so used. For the same reason it is 
often used as a covering for hulls of vessels. Its great 
conductivity for electricity together with its tenacity 
gives it use for wiring houses for electric lighting, for 
telephone circuits and a great variety of other electrical 
uses. Being an excellent conductor of heat renders it 
valuable for stills and boilers, and for cooking vessels. 
It is almost universally used in candy factories, for the 
reason that the syrup scorches much less readily in a 
copper vessel than in most others. This is because the 
heat is distributed quickly and evenly over the surface, 
while in an iron vessel, or one of porcelain ware, the 
bottom is very much hotter than the sides. In large 
establishments where great quantities of food must be 
prepared as in asylums and penitentiaries, or in res- 
taurants like the railway eating houses where the service 
must be very rapid, copper vessels are used almost ex- 
clusively. Such vessels would probably find use also in 
the home were it not for the fact that/ while such strong 
acids as sulphuric and hydrochloric are not decomposed 
by copper, it does react with many fruit acids, such as 
those found in tomatoes, apples and the like. Since 
the compounds resulting are poisonous, it is not desira- 
ble. In large establishments, such of the vessels as are 
used with acid foods are "tinned" on the. inside. As 
this wears off it has to be replaced. In the form of al- 
loys, copper is used in large quantities. Gold and silver 
coins are 10 per cent copper; brass contains zinc and 
copper, a common variety having 65 per cent of the for- 
mer to 35 of the latter. Bronze consists of copper and 
tin; German silver of copper zinc and nickel. 



366 APPLIED CHEMISTRY 

5. Blue Vitriol. — This compound of copper, often called 
blue stone, is mainly a by-product of the large gold and 
silver refineries. Small portions of copper in the form 
of a sulphide occur mixed with the other metals; 
in a specially constructed furnace to which air is ad- 
mitted the copper sulphide is oxidized to copper sulphate. 
This is treated with water and dissolved out, is filtered 
and evaporated to the point of crystallization. Formerly, 
a very considerable portion of that used in the United 
States was made in the Argentine smelter at Kansas 
City, with a monthly output of 1,800 tons. After the 
consolidation of the various refining companies, this 
work was transferred to the plants at Omaha and Den- 
ver. Blue vitriol crystallizes with five molecules of 
water. Exposed to the air it gradually loses this, be- 
comes white and crumbles to a powder. By adding wa- 
ter the color is restored, and upon crystallizing the 
pentahydrate is again obtained. Its solution gives an 
acid reaction with litmus owing to hydrolysis. (See p. 
313.) Like other salts of copper it is very poisonous. 

6. Electrotyping. — Blue vitriol is used extensively in 
making electrotypes for printing books and magazines. 
The type is set up, proof read and locked in a frame 
or "form" the size of the page to be printed. An im- 
pression of this is taken in a sheet of prepared wax and 
this is covered with finely powdered graphite to make it 
a conductor of electricity. This is then suspended at the 
cathode in a solution of blue vitriol. A sheet of copper 
forms the anode (Fig. 63). "When the battery is con- 
nected, copper is slowly deposited upon the graphite 
covered face of the wax. When the deposit has attained 
the thickness of a good visiting card, the sheet is re- 
moved from the solution, washed thoroughly and dried. 
Molten type metal is then poured upon the back of the 



THE COPPER GROUP 



367 



copper. This melts off the wax and gives a copper plate 
the exact duplicate of the lead type used to make the 
imprint upon the wax. All books are printed from 
such electrotypes; likewise, "patent" advertisements 
which are run in the large dailies of all the cities, and 
wherever a very large number of copies is desired. Lead 
type is so brittle that it will permit of only a relatively 
limited number of impressions with perfect results. By 
a similar method is made pure electrolytic copper for 
which in limited amounts there are many demands. To 
obtain this the impure copper is suspended from the 




copper 
jfrip • 



-wax 
j beef 



CuS0 4 j-olufior? 



V2ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZA 



Fig. 63. — Making an electrotype. 



anode and a very thin sheet of pure copper at the cathode. 
As the copper ions from the blue vitriol solution deposit 
upon the thin sheet at the cathode, the sulphate ions 
dissolve the impure copper bar at the anode and thus keep 
the vitriol solution concentrated. Thus, gradually, all 
the copper at the anode may be transferred to the cathode 
where it is deposited pure electrolytic copper, while the 
impurities remain in solution or precipitate out. Blue 
vitriol has also found wide use in "crow-foot" and other 
similar wet batteries for telegraphic work ; its use in pre- 
venting the growth of algae in water reservoirs has been 



o68 APPLIED CHEMISTRY 

mentioned. It is also used extensively for making bor- 
deaux mixture for spraying trees. 

7. Some Other Compounds. — Copper forms many other 
salts : for example, cupric chloride. CuCl 2 .2H 2 of a 
beautiful turquoise blue color: cupric nitrate. Cu(X0 3 ) 2 
.6H 2 0. dark blue in color, and very deliquescent: cop- 
per acetate. Cu(C 2 H 3 2 ) 2 H 2 0, green in color. It also 
forms cuprous salts, such as cuprous chloride. Cu 2 Cl 2 . 
white in color, and very unstable. In the presence of 
air and moisture this rapidly takes up oxygen and forms 
a basic cupric chloride. There are two oxides, cupric 
and cuprous, with the formulas. CuO and Cu 2 0. The 
former is black and the latter red in color. 

8. Occurrence of Silver. — Silver is often found free, 
sometimes in nuggets of considerable size. Most copper 
ores contain more or less silver, but the greater part 
of our supply is obtained from the lead smelters in the 
treatment of argentiferous lead ores. 

9. Characteristics of Silver. — Silver is one of the whit- 
est of the metals and the best in conductivity. It has 
a melting point of about 960° C. a little more than 100 
below that of copper. It does not oxidize in the air 
at any temperature, but readily reacts with hydrogen 
sulphide. As this frequently occurs in the air from the 
combustion of coal or coal gas. or from the decomposi- 
tion of various proteins containing sulphur, silverware 
commonly becomes tarnished. "While silver will not com- 
bine with oxygen even at high temperatures, above its 
melting point, it will o.~b$or~b more than twenty times its 
own volume of oxygen from the air. When solidification 
takes place this occluded oxygen is given off again rap- 
idly, causing the silver surface to "spit" and become 
rough. It is even more ductile than copper, such that 
wires a mile and a quarter in length will weigh only about 



THE COPPER GROUP 369 

1 gram. Silver is not attacked by alkalies or by hydro- 
chloric acid or cold sulphuric. Nitric acid is readily de- 
composed and also boiling-hot, concentrated sulphuric. 

10. Uses of Silver. — Everyone is familiar with the 
uses of silver. Thermos bottles and Dewar bulbs, men- 
tioned elsewhere, and the better class of mirrors are 
silvered by the reaction of a reducing agent with a sil- 
ver salt. Formaldehyde or Rochelle salt in the presence 
of an alkali is often used for this purpose. The process 
may be easily illustrated. If a few cubic centimeters 
of a solution of silver nitrate be put into a test tube and 
ammonium hydroxide added drop by drop until the 
brown precipitate which forms at first is just dissolved, 
upon adding a little tartaric acid and warming, the tube 
on the inside is beautifully silvered. Our silver coins are 
90 per cent silver. "Sterling" silver does not mean, as 
many suppose, pure silver, but of the same degree of 
fineness as English coins, which are 925 parts of silver 
to 75 of copper. Most of the silverware in common use 
is merely some harder metal or alloy plated with silver. 
The process is the same as that described for copper 
plating. A sheet of silver is suspended at the anode and 
the article to be plated at the cathode. A solution of 
potassium silver cyanide takes the place of the copper 
sulphate. In the case of silver, the nitrate, the most 
common silver salt, does not give a deposit that adheres 
well. 

11. Silver Nitrate, AgN0 3 . — This compound may be 
prepared by dissolving silver in nitric acid. Nitric 
oxide and water are the two other products formed, as 
is usually the case when a metal decomposes nitric acid. 
This is seen in the equation, 

3Ag + 4HN0 3 -> 3AgN0 3 + NO + 211,0. 
Silver nitrate crystallizes in thin, flat plates, rhombic in 



370 APPLIED CHEMISTRY 

shape, colorless and transparent. Commercially, it is 
sold for medical purposes in small round sticks under 
the name "lunar caustic." These usually contain a 
small percentage of silver chloride. It has caustic prop- 
erties and is used for this reason in cauterizing wounds, 
such as dog bites, and others presumably infected. In 
solution it is sometimes used for sore throat and other- 
wise as an antiseptic. Exposed to light, especially in 
contact with organic matter, it turns dark. On this 
account it is a constituent of many indelible inks used 
in laundry marking; also of most hair dyes, and as the 
source of the silver compounds used in photography. 

12. Silver Chloride, AgCl. — If a solution of common 
salt be added to one of silver nitrate, silver chloride is 
produced, thus, 

AgN0 3 + NaCl -» AgCl + NaN0 3 . 

It is a curdy white precipitate, especially if shaken vig- 
orously ; it rapidly turns dark when exposed to sunlight. 
It is very soluble in ammonium hydroxide, forming a 
complex silver salt resembling the hydrates. Thus, 

AgCl + 2NH 4 HO -» AgC1.2NH s + 2H 2 0. 

Silver chloride is used extensively in preparing one class 
of photographic papers which will be studied later. 

13. Silver Bromide, AgBr. — This compound is made 
by adding to a solution of silver nitrate one of potassium 
or ammonium bromide, thus, 

AgN0 3 + NH 4 Br -> AgBr + NH 4 N0 3 . 

It is a very pale-yellow precipitate, much less soluble 
in ammonium hydroxide than is the chloride. It is much 
more sensitive to light. For this reason it is employed in 
photography for very rapid work both on plates and 
films, as well as for papers and enlargements. 



THE COPPER GROUP 371 

14. Photography. — Most everyone is interested more 
or less in photography, yet but few do much more than 
"press the button." In sensitizing plates and films a 
solution of silver nitrate and one of ammonium or po- 
tassium bromide are added to one of gelatine, whereupon 
the reaction shown above takes place. The emulsion is 
kept warm until the silver bromide has formed a fine 
precipitate throughout the entire mass, after which it 
is allowed to solidify. The mass is then cut into shreds 
and treated with cold water to dissolve out the ammo- 
nium nitrate which was formed as a by-product. It is 
then dried, melted and allowed to flow over the plate, 
forming a thin film. Most photographic papers used by 
amateurs are made in a similar way and contain the 
silver bromide in a thin film upon the paper. On ex- 
posure to light, plates and papers, containing silver bro- 
mide in the film, show no results. The plate is put into a 
solution of some reducing agent, more often now a coal 
tar product such as metol or hydroquinon, together 
with an alkaline salt such as sodium carbonate. The re- 
ducing agent acts upon the silver salt, decomposes it 
and sets the silver free. This occurs much more rapidly 
where the light has already begun the process. The 
operation is called developing the plate. Naturally, such 
portions of the landscape, or object being photographed, 
as reflect considerable light will affect the silver bromide 
the most, and upon developing will have the silver reduced 
most rapidly, hence will become dark. For this reason, 
since white objects appear upon the plate as black after 
development, it is spoken of as a negative. If the plate 
be allowed to remain in the developer indefinitely finally 
all the silver is reduced and the plate becomes black all 
over. To prevent this, at the proper time, known usually 
by the image beginning to appear upon the reverse side of 



372 APPLIED CHEMISTRY 

the plate, it is removed from the developer, rinsed and 
put quickly into a solution of sodium thiosulphate, called 
"hypo." This is an excellent solvent for silver chloride 
and bromide, so that any portions of these salts left un- 
reduced by the developer are dissolved out and thus the 
reduction and darkening; of the plate is stopped. This is 
called fixing the plate. The process is complete when on 
being held up to the light no white appears anywhere and 
the plate is more or less transparent. Developing is 
done under red light. Students of physics know that 
sunlight consists of three kinds of rays — light, heat and 
chemical rays. In a study of the spectrum it has been 
found that most of the heat rays are at the red end 
and most of the chemic at the violet end of the spectrum. 
Therefore, light passed through red glass or other red 
objects has most of the chemic rays filtered out. Hence, 
the sensitized plate is not affected by such light. 

15. Printing-Out Papers. — There are two kinds of pa- 
pers used in photography in making the prints. Print- 
ing-out papers have a film containing silver chloride which 
is not nearly as sensitive to light as silver bromide. They 
are placed in a printing frame under the negative and ex- 
posed directly to good sunlight. The image prints out' 
slowly and can be seen as it appears. When the proper 
degree of intensity has been reached it is fixed and toned. 
The fixing is with hypo as already described. The toning 
is done with gold or platinum compounds in which small 
portions of these metals take the place of an equivalent 
amount of silver and give a richer and softer print. The 
' ' proof ' ' which the photographer furnishes is on printing- 
out paper and has not been fixed or toned. Hence, it is 
not permanent, and exposed to light soon darkens all over. 

16. Developing Papers. — Developing papers, such as 
velox, argo, and many others now largely advertised, 



THE COPPER GROUP 373 

contain silver bromide in the film of gelatine. They are 
intended to be printed by artificial light and if used in 
daylight it must be very much subdued and the exposure 
of the briefest possible time. No image appears upon ex- 
posure, but it must be brought out as with plates and films 
by developing. This fact gives to such papers the name 
developing papers. With ordinary electric light an ex- 
posure of from ten to thirty seconds, depending upon the 
negative, soon learned by a little practice, is usually suffi- 
cient. The developing is in the usual way, but a stronger 
solution is used and the image must come up quickly and 
sharply ; if it does not, the paper becomes stained and the 
picture ruined. It is quickly transferred to the fixing 
bath and after a few minutes to a tray of water where it 
must be washed thoroughly. 

17. Blue Prints. — Blue prints, used somewhat for 
landscape work, but mostly by architects and engineers, 
are not made from silver compounds, but from iron. 
However, they will be considered at this time. A good 
grade of paper in a room with subdued light is brushed 
over with a solution of ferric ammonium citrate. This 
gives to the paper on the one side a pale-yellow color. 
For use it is exposed under a negative or architectural 
drawing to direct sunlight, since it is not very sensitive. 
When the proper exposure has been made, which may be 
known by a sort of bluish-bronze appearance, the paper 
is removed from the frame, and submerged in water. 
Wherever the sunlight has been able to pass through the 
negative or drawing it has reduced the ferric citrate to a 
ferrous salt, blue in color and not soluble in water. The 
water, therefore, washes out the unchanged yellow ferric 
citrate and leaves the blue in the paper. Hence, in an 
architectural drawing since the original lines are in black, 
in the print they will be white upon a blue background. 



o/4t APPLIED CHEMISTRY 

Blue print paper may easily be prepared by the student 
for his own use in the laboratory. Blue prints are so 
simple and so easily prepared that many attempts have 
been made to change them into sepia or black by the 
application of some reagent. Most formulas, however, 
in the hands of the amateur give rather indifferent and 
unsatisfactory results. 

18. Occurrence of Gold. — As a rule gold occurs free in 
nature; in Colorado, however, it is sometimes found in 
combination with tellurium as gold telluride. Originally, 
probably, the grains or nuggets were scattered through 
veins of quartz found in cracks in the earth's crust. How- 
ever, as erosion took place, the disintegrated particles of 
rock and gold have been carried down till now they are 
found in river beds and alluvial deposits in many places. 

19. Mining of Gold. — The early history of every gold 
field is largely the same. The prospector recovers the 
coarser particles of gold by "panning" or "cradling." 
This consists in washing out by a rocking motion, usually 
in a stream of water, the sand and lighter particles. 
From the heavier particles remaining in the cradle will be 
obtained, by hand, the grains and nuggets of gold. 
When the field becomes proved as a valuable producer, 
capital comes in with dredging or hydraulic mining. In 
the latter, streams of water, brought from distances up 
in the mountains under tremendous pressure, are directed 
against the hillsides and other gold bearing deposits, 
which are thus disintegrated and washed down. The 
whole is made to flow through troughs or flumes over fre- 
quently recurring pockets of mercury or over copper 
plates amalgamated with mercury. In this way, the gold 
particles are caught by the mercury and at intervals the 
mercury is distilled and recovered for use again. In 
California large quantities of gold have been recovered in 



THE COPPER GROUP 375 

this way; but from the fact that the great volume of 
water used has resulted in washing; down over good agri- 
cultural lands immense quantities of sand and gravel, 
much litigation has resulted in recent years with the aban- 
doning of such methods in many places. (Fig. 64.) 
Dredging is usually employed for working deposits along 
river beds. For the purpose, a boat of considerable size is 
constructed upon the land to be dredged near some river 
or water supply. A pond is dug large enough to contain 
the boat and the water turned in to fill it. A steam or 











: * 


*■* '^ 


At) 




iL^pP -8*~ 


""..,;■•;'"■■ 


'■>' 


9HH 


B^^^*^f^ ■ ' &ffi£P3* i 




WsSm 




EL ^^^"Sfcf *" 












. 


&■■ -^3f i*"g) JijB&jjST'Wi 


lOowii B^v^jsfe^j 


• " '•"* 






• 



Fig. 64. — Hydraulic mining. (From Cook's "A Practical Chemistry.") 

motor shovel, such as is used for extensive excavation 
work, is erected at one end of the boat. This scoops out 
the gravel in front of the vessel, swings it around upon 
the deck and dumps it where streams of water provided 
by pumps wash it off at the stern over amalgamated cop- 
per plates. The gold is caught by the mercury as already 
explained. Thus the pond is constantly being filled in the 
rear and dug out in front of the boat. Large tracts of 
alluvial deposits are worked in this way with very profita- 



376 APPLIED CHEMISTRY 

ble results. One of the best known sections in the Califor- 
nia fields is that at Oroville. "Quartz vein mining" 
is the term applied to that used when tunnels are 
run or shafts sunk to follow the veins of gold-bearing- 
quartz. In such cases, as the rock is brought to the surface 
it is sorted by hand and the portions containing little or no 
gold are carried by small cars to the dump and constitute 
the ' ' tailings. ' ' The quartz containing the gold is crushed 
and the gold recovered either by the chlorination or the 
cyanide process. In the former, the quartz rock is 
roasted, which serves to bring the gold to the surface or 
if it be in the form of the telluricle, to volatilize the tellu- 
rium and leave the gold free. It is then dissolved by liquid 
chlorine or by treatment with bleaching powder mixed 
with hydrochloric acid. From the solution of gold chlo- 
ride thus obtained the metal is recovered by precipitating 
with ferrous sulphate or oxalic acid. If the cyanide proc- 
ess is used, roasting is not necessary. The gold is dissolved 
in a solution of potassium cyanide and precipitated from 
this by zinc. In many places stamp mills are now used. 
They consist of steel cylinders of considerable size and 
weight held upright by supports. They are continually 
lifted by machinery and dropped automatically upon the 
quartz, which is slowly fed upon the platform or table. 
The continued ' ' stamping ' ' crushes the rock into fine par- 
ticles ; a stream of water washes it over amalgamated 
plates and it is recovered as in the case of dredging. 

20. Characteristics of Gold. — Gold is a soft, yellow 
metal with a specific gravity of 19 and melting point 
about 1,060° C. It is thus between that of silver and cop- 
per. It is the most malleable of all metals and in the 
form of gold leaf is beaten so thin that it is said 1,500 
sheets together are no thicker than an ordinary sheet of 
writing paper, Gold is the least active chemically of 



THE COPPER GROUP 377 

the more familiar metals. It is not attacked by oxy- 
gen or tarnished by hydrogen sulphide in the air as is 
silver. It is soluble in aqua regia in which it forms 
gold chloride, AuCl 3 . It is also soluble in potassium 
cyanide by which a complex potassium auric cyanide is 
produced, KCN.Au(CN) 3 . Nothing need be said re- 
garding the uses of gold. When pure it is spoken of as 
twenty-four carats fine. Ordinary jewelry is not over 
fourteen carats and may even run as low as ten without 
being objectionable. Gold plating, or gilding, uses a 
cyanide solution and the process is similar to that al- 
ready described for copper and silver. American gold 
coins are 90 per cent gold and 10 per cent copper. 

Exercises for Review 

1. Name the metals of the copper group and state their position 
in the periodic table. What is meant by a long period in the 
table? 

2. What is a noble metal? 

3. Describe the deposits of copper in the north; in the west. 
Name some important ores and give composition. 

4. Give the characteristics of copper. 

5. Name the most important uses of copper and state why so 
used in each case. 

6. Name three alloys of copper and give composition. 

7. Give formula for blue vitriol and state how made. 

8. Explain how an electrotype is made. What advantage is 
there in an electrotype? Give uses for them. What is electrolytic 
copper? How made? 

9. Name some other compounds of copper with formulas. 

10. What is the source of most of our silver? 

11. Give chief characteristics of silver. 

12. Name some familiar uses for silver. How are mirrors made? 

13. How is silver nitrate made? What is its commercial name? 

14. Give characteristics of silver nitrate. Also its chief uses 
and state the principle underlying each use. 

15. How is silver chloride made? Use? 

16. How is silver bromide made? What use has it? 

17. How axe photographic plates find films made? 



3/8 APPLIED CHEMISTRY 

18. "What is a negative? Why so called? 

19. Explain the process of developing a plate. 

20. Name two kinds of photographic papers. What is the dif- 
ference between them in action and composition? 

21. Give process of making a print on each kind of paper. 

22. In what does fixing a negative consist? What reagent is 
used for doing this? 

23. What is the sensitizing agent in blue print papers? What 
happens when they are exposed to the light ? What does the wa- 
ter do? 

24. What can you say of the occurrence of gold? 

25. What is meant by panning? By hydraulic mining? 

26. Describe dredge boat mining. How is the gold recovered? 
What becomes of the mercury? 

27. Of what does the chlorination process consist? 

28. G-ive the chief characteristics of gold. 

29. What are the two best solvents of gold? 

30. How is an article gold plated? 

31. What is meant by gold eighteen carats fine? 

32. What is the carat of the five dollar gold coin? 



CHAPTER XXXI 
THE MAGNESIUM FAMILY 



Outline — 



Members of the Group 
Magnesium 

(a) Natural compounds 

(6) Characteristics of 

(c) Uses 

(d) The Oxide 

(e) Other Compounds 
Zinc 

(a) Ores of 

( b ) Eeduction 

(c) Characteristics of Zinc 

(d) Uses 

(e) Zinc Sulphate 
(/) Zinc Chloride 
(g) Zinc Oxide 

Mercury 

(a) Occurrence 
(&) Characteristics 

(c) Uses 

(d) Mercuric Oxide 

(e) The Chlorides 
(/) Vermilion 

1. General Comparison. — Besides magnesium, beryl- 
lium, also known as glucinum, zinc, cadmium and mer- 
cury belong to this group. Beryllium is the lightest 
with an atomic weight of 9.1 and mercury the heaviest 
with a weight of 200. They all form compounds with 
a valence of two, and with the exception of mercury 
form no other series. Magnesium in some of its reac- 
tions resembles calcium and in analytic separations is 
often classed in that group. 

379 






380 APPLIED CHEMISTRY 

2. Natural Compounds of Magnesium. — Besides the 
sulphate found in sea water and in springs, known as 
Epsom salt, magnesium chloride, MgCl 2 , is found asso- 
ciated with common salt, and the double carbonate of 
magnesium and calcium, known as dolomite, occurs with 
limestone. Magnesium also is found in several natural 
silicates of more or less complex composition. One of 
the best known of these is meerschaum. It is a soft, 
white mineral used in making pipes for which it is 
prized because of the brown colors it assumes. Much 
more valuable than this is asbestos, a greenish, anhy- 
drous silicate. 

This mineral has a silken luster and is fibrous, so that 
by mechanical process it may be worked into a loose 
mass. In this form it has numerous uses. Mixed with 
magnesium oxide it is employed as an insulating ma- 
terial for steam pipes to prevent loss of heat by radia- 
tion; railway locomotives are thus jacketed; it is used 
for insulation against fire in many ways ; for large stage 
drop curtains; in stoves; about furnaces and furnace 
pipes; in gaskets for steam pipe fittings; brake linings 
for motor cars; as a cement for expensive stucco work; 
imitation tile and shingle roofing and in scores of other 
ways. 

3. Characteristics of Magnesium. — Magnesium is pre- 
pared much as is calcium, that is, by the electrolysis of 
the double salt of magnesium and potassium, KC1. 
MgCl 2 . It is a grayish white metal, with a specific 
gravity of 1.75. In the air it reacts slowly with oxygen 
by which a thin coating upon the surface is formed. 
When heated it burns vigorously with a brilliant white 
light. It is one of very few elements which combines 
directly with nitrogen. When burned in the air an ap- 
preciable amount of the product formed is magnesium 



THE MAGNESIUM FAMILY 381 

nitride, Mg 3 N 2 . Magnesium does not react with cold 
water, but will set free hydrogen from boiling hot water. 
It is high in the electromotive series of metals and rap- 
idly decomposes even dilute acids with evolution of hy- 
drogen. It is brittle, but when heated somewhat it may 
be drawn into wires ; flattened, this is spoken of as mag- 
nesium ribbon. It is also sold in the form of powder. 

4. Uses of Magnesium. — The powdered magnesium is 
used extensively for flashlight work in photography. 
For this purpose, sometimes it is blown into the flame of 
a specially constructed alcohol lamp ; again it is mixed 
with potassium chlorate, which causes a very rapid com- 
bustion of the whole mass. The same mixture is used in 
fireworks to give the intensely white lights in the vari- 
colored bombs. Flashlight powders must be regarded 
as explosives and handled with great care. Magnalium 
is an alloy of magnesium and aluminum, light and tena- 
cious in properties, at present being made for use in 
air ships and for similar work where a light metal is 
needed. 

5. Magnesium Oxide, MgO. — This is sold under the 
name of magnesia. It is a fine, white powder, made by 
calcining magnesium carbonate, as lime is prepared from 
limestone. The reaction is the same, 

MgC0 3 -» MgO + C0 2 . 
It is an excellent insulating material against loss of 
heat. Hence, as stated elsewhere, it is mixed with as- 
bestos, about four parts to one, as a covering for steam 
pipes and all similar places where loss of heat is to be 
prevented. Our great railway locomotives, in cold weath- 
er, would never be able to make sufficient steam to 
pull a loaded train were it not for the heavy jacketing 
of the boilers with magnesia. Likewise, in refrigeration 
systems, the pipes which transmit the brine from the 



382 APPLIED CHEMISTRY 

source to points of use are protected against access of 
outside heat. For a similar reason, and because it is 
infusible, it is used in lining electric furnaces and for 
making crucibles where great heat is to be employed. 

6. Other Compounds. — Magnesium sulphate, sold un- 
der the name of Epsom salt, is a light crystalline solid, 
with the formula MgS0 4 .7H 2 0. It is somewhat efflo- 
rescent. The use of the salt in medicine as a purgative 
is well known. It is also sometimes used in weighting 
cotton goods. Magnesium carbonate as prepared in the 
laboratory is a basic salt, having the formula MgC0 3 . 
Mg(HO) 2 . This is because of the hydrolysis which 
takes place. It is a fine, white powder often used in 
tooth pastes and in metal polishes. The chloride, 
MgCl 2 , has been mentioned as a deliquescent salt, found 
in sea water, causing the dampness often observed in 
table salt. 

7. Occurrence of Zinc. — The greater portion of the 
supply of zinc in the United States is obtained from 
the Joplin district, which includes not only southwest 
Missouri, but southeast Kansas and northeast Oklahoma. 
It occurs in this section as a sulphide, ZnS, known locally 
by the name of "jack" but scientifically as sphalerite 
or zinc blende. In some parts of the district it is mixed 
with a lead ore, galena, also a sulphide. In several of 
the Western States, for example, Colorado and Mon- 
tana, zinc occurs mixed with copper and silver ores, 
usually as a sulphide ; in some of the Eastern States it 
occurs as franklinite, ZnO.Fe,0 3 . 

8. Reduction of Zinc Ores. — Several of the metals 
thus far studied, notably the silver group, are either 
found free or may be reduced by heat alone. Some of 
the copper ores, because of their complexity and mixture 
of other metals, require special treatment, but even 



THE MAGNESIUM FAMILY 383 

many of these may be reduced by heat alone. Most of 
the other metals studied thus far are reduced electro- 
lytically. Zinc introduces a third type, those which re- 
quire the aid of some reducing agent, such as carbon. 
The process will be considered very briefly. As carbon, 
even when heated, does not combine readily with sul- 
phur, it becomes necessary to convert the zinc ores into 
an oxide. This is done by a process known technically as 
"roasting." The term means heating strongly with a 
plentiful supply of air. By this process the sulphur and 
zinc both are converted into oxides, thus, 

2ZnS + 30 2 -> 2S0 2 + 2ZnO. 
The zinc oxide is next mixed with coke, heated strongly 
in cylindrical retorts made of fire clay. The zinc dis- 
tils out in the form of vapor and is condensed. 

9. Characteristics of Zinc. — Zinc is a bluish- white 
metal with a melting point of about 420° C, and boiling 
point of 950° C. It wull be seen that a temperature suffi- 
cient to melt silver will vaporize zinc. "Spelter," as 
the product from the zinc smelters is called, is brittle; 
but if heated, at a temperature between 125° and 150° 
C, it becomes malleable. Rolled into sheets at this 
temperature its malleability becomes permanent. It is 
a poor conductor of heat and electricity. It is only 
slightly attacked by the air, for the basic carbonate 
which forms upon the surface is closely adhering and 
protects the metal almost as if painted. Water is not 
decomposed by zinc, but dilute acids are readily, with 
the evolution of hydrogen. This is especially true of 
commercial zinc which is somewhat impure. Molten zinc 
mixes readily with silver, copper, tin and antimony, 
but not with lead or bismuth. Melted with lead it will 
float as ether upon water with only a small quantity 
of each dissolved in the other. This fact is employed 



o84 APPLIED CHEMISTRY 

in separating silver from lead when obtained from ar- 
gentiferous lead ores. 

10. Uses. — Because of its nonconductivity it is often 
used for lining refrigerators and beneath or behind 
stoves to protect the floors or walls. Its most extensive 
use, probably, is for "galvanizing" iron. This is not 
done electrolytically as the name might imply, but by 
dipping the heated iron, previously well cleaned, into 
molten zinc. Upon withdrawing the iron a coating of 
zinc adheres. Practically all iron wire fencing is now 
made in this way. Galvanized sheet iron is used for 
gutters, downspouts, cornice work, granaries, wind 
mills, feed and watering troughs, as well as for countless 
smaller articles. Dry cells consist of a container made 
of zinc which serves as the positive plate, a carbon rod 
at the center as the negative, and a packing, in part, 
of sal ammoniac or some other salt which reacts with 
the zinc. Many valuable alloys of zinc are familiar. 
Brass and German silver have already been mentioned. 
Some "white" metals, from which various articles of 
plated silverware are made, are an alloy of copper and 
zinc in which the proportion of zinc is high, to such an 
extent that the color of the copper is not apparent at all. 

11. Zinc Sulphate, ZnSO^.lK.O.— Commercially this 
compound is known under the name of white vitriol. It 
contains the same quantity of combined water per mole- 
cule as magnesium sulphate. It may be prepared by 
treating zinc with dilute sulphuric acid or from the native 
blende in a similar manner. Like magnesium sulphate it 
is efflorescent. It is used somewhat as a mordant and to 
some extent as an antiseptic in medicine. A mordant is 
a reagent which has the power of fixing a dye in the fibers 
of a cloth so that it is not easilv removed by water. 



THE MAGNESIUM FAMILY 385 

12. Zinc Chloride, ZnCl 2 . — This is a white compound 
which may be prepared by treating zinc with dilute 
hydrochloric acid in slight excess and boiling to dry- 
ness. It is very deliquescent and in solution gives an 
acid reaction owing to partial hydrolysis. For this rea- 
son it is commonly used in soldering as a flux to give 
a clean surface. The free hydrochloric acid in the solu- 
tion dissolves the film of oxide always present, so that the 
melted solder may come into direct contact with the metal. 
Melted zinc chloride has the remarkable property of be- 
ing able to dissolve cellulose ; by dipping sheets of paper 
into the liquid, parchment is made. 

13. Zinc Oxide, ZnO. — As usually obtained, zinc oxide 
is a faintly yellow compound. Perfectly pure it is white 
when cold, but distinctly yellow when hot. It is a valua- 
ble by-product of many smelters, being obtained by the 
roasting of ores containing a very small percentage of 
zinc. The oxide is vaporized and carried over with the 
sulphur dioxide and other gases and is condensed in 
large, cool chambers upon coarse sacking. Afterward 
it is purified by continued heating below its point of 
vaporization. It is used extensively in the manufacture 
of paints and enamels. Ground in oil the former is 
sold under the trade name of "zinc white." Small 
quantities of the oxide, carefully purified, are used in 
pharmacy for making salves and other applications for 
skin diseases. Its action is probably largely antiseptic. 
It is also used in dentistry in making temporary fill- 
ings for teeth, especially for children. For this purpose 
it is mixed with glacial phosphoric acid (p. 280) to form 
a soft mass which is placed in the prepared cavity. It 
very soon hardens much as does plaster of Paris, form- 
ing an oxyphosphate of zinc. This oxide is of interest, 
for the reason that it possesses a dual character, serv- 



386 APPLIED CHEMISTRY 

ing sometimes as if basic and again as if acidic. In the 
hydrated form, Zn(HO) 2 , it readily dissolves in dilute 
acids, forming zinc salts, in which zinc is the posi- 
tive ion. On the other hand, it will dissolve, though 
somewhat less readily, in strong bases, such as sodium 
hydroxide. It then forms salts called "zincates" in 
which zinc is found in the negative ion. Thus, 

2HCl + Zn(HO) 2 -> ZnCl 2 + 2H 2 0, 
2NaHO + Zn(HO) 2 -> Na 2 Zn0 2 + 2H 2 0: 

In these cases the zinc hydroxide evidently has ionized 
as follows, 

Zn(HO) 2 ±5 H 2 Zn0 2 ±± Zn - (HO) (HO) + II,H - Zn0 2 . 
Therefore, although zinc hydroxide is but slightly solu- 
ble in water, such portions as do dissolve are evidently 
ionized in both ways in fixed definite amounts. From 
the location of zinc in the periodic table, not far from 
the diagonal, such behavior might be expected. 

14. Occurrence of Mercury.— Mercury has been known 
at least since 300 B.C. when it was prepared by Theo- 
phrastus, who gave it the name meaning liquid sih'er. 
Its symbol is derived from the Greek word, hydrargyrum. 
It is found in comparatively small quantities and in few 
places in the world. In America the mines in central 
California are the most productive. In Europe, Spain 
and Austria produce the greater part. In all cases the 
sulphide, HgS, known as cinnabar, with some inter- 
mingled free mercury, is the ore found. From this the 
mercury is obtained by distillation. 

15. Characteristics of Mercury. — Mercury is the only 
metal, liquid at ordinary temperatures. It becomes a 
solid at about -39° C. and boils about 360°. In the solid 
form mercury is somewhat malleable and to a consid- 
erable extent resembles lead. It dissolves or allovs 



THE MAGNESIUM FAMILY 387 

readily with many of the other metals, especially gold, 
silver, copper, tin and zinc. Such alloys are called amal- 
gams. They may be obtained by putting the finely di- 
vided metals into mercury, or a surface amalgamation 
may be had by dipping the clean metal into a solution 
of some salt of mercury. A bit of clean gold dropped 
upon mercury will sink and dissolve as a lump of sugar 
in a cup of hot water. Again, a clean penny in a solu- 
tion of mercuric nitrate soon takes on a coating of mer- 
cury which upon slight rubbing has the appearance of 
burnished silver. In the latter case an amount of cop- 
per has dissolved equivalent to the mercury deposited, 
that is, one atomic weight of copper has been dissolved 
for each atomic weight of mercury deposited. Mercury 
is not tarnished by the air, nor does it set free hydrogen 
from acids It decomposes nitric acid and boiling sul- 
phuric with the usual results in such cases. The two 
equations following indicate the reactions, 

3Hg + 8HN0 3 -^ 3Hg(N0 3 ) 2 + 4H 2 + 2NO, 
Hg + 2H 2 S0 4 -* HgS0 4 + 2H 2 + S0 2 . 

16. Uses of Mercury. — The use of mercury for amalga- 
mating copper plates and otherwise in obtaining gold has 
been described. (See p. 374.) It is used in thermometers 
and to some extent in barometers, although the aneroid 
is taking the place of the mercurial barometer in many 
places. The advantages of mercury in thermometers 
are that it has a high and uniform rate of expansion 
through a lone: range of temperature and is of high 
boiling point. Alcohol thermometers are valuable for 
use below the freezing point of mercury. Zinc plates 
in galvanic batteries are commonly amalgamated to 
prevent local circuits with rapid wasting of the metal. 
In dentistry amalgam fillings, consisting of silver and 
tin with sufficient mercury to form a soft pliable mass. 



388 APPLIED CHEMISTRY 

are commonly used except for front teeth. This amal- 
gam has the property of setting rapidly and of retaining 
its color, while dental amalgams containing cadmium, 
a metal formerly used considerably, turn dark and be- 
come unsightly. 

17. Mercuric Oxide, HgO. — This is a heavy solid, crys- 
talline or amorphous, yellow, orange or red in color, 
according to the method by which it is obtained. The 
yellow is obtained by treating a warm solution of mer- 
curic chloride or of some other mercuric salt with sodium 
or potassium hydroxide solution, in slight excess. The 
hydroxide, formed at first, quickly decomposes into mer- 
curic oxide and water, thus, 

HgCl 2 + 2KHO ->Hg(HO) 2 + 2KCl-> HgO + H 2 + 2KCL 

It is regarded as the same chemically as the orange or 
red variety but in a finer state of division, since by 
trituration the red variety changes to yellow. It is used 
somewhat in medicine in the form of salves, mainly on 
account of its antiseptic properties. 

18. Mercurous Chloride or Calomel, Hg 2 Cl 2 . — This is 
a finely divided white powder used in medicine. It is 
easily prepared in the laboratory by treating a solution 
of mercurous nitrate with a solution of common salt or 
hydrochloric acid, thus, 

Hg 2 (N0 3 ) 2 + 2NaCl -* Hg 2 Cl 2 + 2NaN0 3 . 

As it' is insoluble in water it is easily separated by filtra- 
tion. On a large scale it is made by mixing common 
salt, mercury and mercuric sulphate intimately and dis- 
tilling. The calomel passes over as a vapor and is con- 
densed'. It is apt to contain small quantities of the mer- 
curic 1 chloride and should be freed from it by washing. 
Like all salts of mercury, calomel is poisonous and all 
the excretory organs are thereby stimulated by its pres- 



THE MAGNESIUM FAMILY 389 

ence. Being an unsaturated compound it tends to take 
up an additional negative ion and form the mercuric 
salt. Therein lies the danger of its use in medicine, that 
of causing mercurial poisoning with consequent saliva- 
tion. With the hydrochloric acid present in the stomach 
or in the presence of acid foods, the mercurous molecule 
begins to change into the mercuric chloride which is much 
more soluble. Its action then upon the system is rapid, 
and before it is eliminated the salivary glands may be 
affected, followed by the well-known soreness of gums 
and teeth. Such instances are not common now, for physi- 
cians, knowing the danger, administer the calomel mixed 
with common soda. This neutralizes the acid in the stom- 
ach and prevents the calomel changing to the soluble 
form. Even as given now, however, acid foods should not 
be used at the same time. 

19. Mercuric Chloride, HgCl 2 . — This is commonly 
known as corrosive sublimate. It is prepared by sub- 
limating a mixture of common salt and mercuric sul- 
phate. It is highly poisonous. The white of eggs is 
regarded as the best antidote, with which the mercuric 
salt forms an insoluble mass. Owing to its poisonous 
properties it is an excellent antiseptic and is frequently 
used for sterilizing surgical instruments and upon band- 
ages for wounds. Applied in this way it is not poison- 
ous. To prevent "scab," a disease which causes a rough 
surface upon potatoes, a dilute solution of corrosive 
sublimate is sometimes used in which the seed potatoes 
are immersed a short time before planting. 

20. Mercuric Sulphide, HgS.— The artificial sulphide is 
sold under the name vermilion. It is a brilliant red pow- 
der, used as a pigment. Prepared in the laboratory by 
adding hydrogen sulphide to a solution of some mercuric 
salt it is a black powder. The reaction is 

HgCL. + ILS -» HgS i 2HC1. 



390 APPLIED CHEMISTRY 

If this black precipitate is sublimed, it changes to the red 
variety. 

Exercises for Review 

1. Name the metals of the magnesium group. Where are they 
located in the table? What is their valence? 

2. Give the important natural compounds of magnesium. What 
are the chief uses for asbestos? 

3. Give the characteristics of magnesium. In what two forms 
does it occur? 

I. What are the principal uses of magnesium? State why so 
used. 

5. What is magnesia? What are its chief uses? 
(5. Give formulas and uses for the sulphate and carbonate of 
magnesium. 

7. Name the important ores of zinc. Where is it mostly ob- 
tained in the United States? 

8. How is zinc blende reduced? Name two other methods of re- 
duction and some metal obtained each way. 

9. Give the most important characteristics of zinc. 

10. What is galvanized iron? Its important uses? 

II. How is zinc sulphate obtained? Its commercial name? 
What other vitriols have been studied? 

12. What is a mordant? 

13. Give method of making zinc chloride. Name some impor- 
tant use. 

14. What is the source of the commercial supply of zinc oxide? 
What is its chief use? 

15. From what are the temporary fillings for teeth made? 

16. Chemically, what point of interest attaches to zinc oxide? 

17. Why will zinc oxide dissolve both in acids and bases? 

18. What is the only ore of mercury? Where found? 

19. Give the important properties of mercury. What is an 
amalgam? How may amalgams be made? Name some uses for 
them. 

20. Give some valuable uses for mercury. 

21. How may yellow mercuric oxide be obtained? What other 
varieties occur? Wherein are they different? 

22. What is calomel? What danger attaches to its use as a 
medicine? 



THE MAGNESIUM FAMILY 391 

23. What is corrosive sublimate? Why so called? What uses 
has it? 

21. How may vermilion be made? Of what use is it? 
25. Complete these equations and state what process is repre- 
sented, 

Mg + 2 — > , 

MgC0 3 (heated) — > , 

ZnO + C -> , 

Zn + HC1 -> , 

ZnO + HO -> , 

HgS + 2 -» , 

Hg 2 (N0 3 ) 2 + NaCl -> , 

HgS0 4 + NaCl + Hg —» , 

HgS0 4 + NaCl -> , 

Hg(N0 3 ) 2 + H 2 S -» . 

Note. — In the above equations the student must supply coeffi- 
cients as needed for proper quantity of each reagent. 



CHAPTER XXXII 

THE ALUMINUM FAMILY 

Outline — 

Members of the Group 
Compounds of Boron 
Aluminum 

(a) Occurrence in Nature 

(b) Precious Stones 

(c) Manufacture of Aluminum 

(d) Characteristics 

(e) Uses 
(/) Alloys 
(g) Alums 

(h) Aluminum Hydroxide 

1. Members of the Group. — Aluminum is the only im- 
portant metal of the family. Boron is a member and 
the lightest with an atomic weight of only 11. It forms 
two compounds of some importance, borax and boric 
acid. The former has been studied under the sodium 
compounds. Boric acid is a white, crystalline solid, 
mildly antiseptic, and frequently used in solution as an 
eye wash. 

2. Abundance of Aluminum.— By referring to Fig. 9 
on p. 52 it will be seen that aluminum constitutes about 
8 per cent of all the matter of the earth, and ranks next 
to silicon in abundance. It is a constituent of all clays 
and of the feldspar rocks from which clays are derived 
by decomposition. Mica, a rock which easily splits into 
thin leaves used in stoves and for insulation in various 
ways, is a silicate of aluminum and potassium. Kaolin, 
Fuller's earth, garnets, sapphires, emeralds, rubies, 
are all aluminum compounds. 

392 



THE ALUMINUM FAMILY 393 

Corundum, an impure oxide of aluminum, ranks next 
to the diamond in the scale of hardness. Emery is of 
the same composition and is familiar to all. It is used 
in various forms as an abrasive: emery powder, grind- 
stones, and emery wheels, whetstones, emery paper and 
emery cloth. Kaolin is a pure white clay used in making 
porcelain ware and the various grades of china. Ful- 
ler's earth is a similar compound used in absorbing the 
coloring matter from vegetable oils such as that made 
from cotton seed. It also has various other uses. 

3. The Precious Stones. — To the mineralogist, rubies, 
sapphires and emeralds are all sapphires. They are crys- 
tallized aluminum oxide, A1 2 3 , and differ from emery 
in that it is uncrystallized and less pure. Their color is 
due to small quantities of another metallic oxide. At 
the present time great quantities of these jewels are being 
manufactured even more perfect than the natural stones 
and with all their characteristics. The white sapphire, 
which resembles the diamond somewhat though less bril- 
liant, is of the same composition as the other sapphires, 
but uncolored. These stones are sometimes spoken of as 
synthetic. For some years, it is said, over nine mil- 
lion carats of rubies and about half as many sapphires 
have been made annually. The garnet is more complex in 
composition than the above stones being an orthosilicate 
of aluminum and calcium, Ca 3 Al 2 (Si0 4 ) 3 . 

4. Preparation of Aluminum. — At the present time alu- 
minum is made by the electrolysis of bauxite, a hydrated 
oxide of aluminum. The principle is the same as used for 
sodium, calcium and several other metals already studied. 
Bauxite, however, does not melt easily, neither does it 
dissolve in water. The problem, therefore, is to secure 
it in liquid form so that it may become a conductor. An- 
other compound of aluminum known as cryolite, a word 



394 



APPLIED CHEMISTRY 



which means ice stone, and given to this mineral because 
of its low melting point, is put into an electric furnace and 
melted. Powdered bauxite is added and dissolves read- 
ily. It will be seen that the cryolite is simply a solvent 
or, as it is technically called, a flux. When the current is 
passed the bauxite decomposes and the aluminum collects 
at the cathode. Fig. 65 illustrates the process. Fresh 
quantities of bauxite are added from time to time as 
needed, the aluminum is drawn off occasionally and the 
process is continuous. The heat generated by the re- 
sistance to the current keeps the cryolite melted. The 
manufacture of aluminum is carried on where cheap 




Fig. 65. — Manufacture of aluminum. 



electric power may be had, especially at Niagara Falls. 
Up to the present time no commercial method has been 
devised for extracting aluminum from such complicated 
compounds as clays. Such a process would be eminently 
desirable. 

5. Characteristics of Aluminum. — Aluminum is a white 
metal, of low specific gravity, being only 2.6 times as 
heavy as water. It is an excellent conductor both of 
heat and electricity. As a given weight of aluminum 
will make a wire of much greater cross section than the 
same weight of copper, it is even better than copper as 
a conductor. In tensile strength it is not greatly dif- 
ferent from copper and most other common metals, ex- 



THE ALUMINUM FAMILY 395 

cept steel, but it has a tendency to crystallize and un- 
protected wires to become somewhat brittle. Its melting 
point is about 700° C. At ordinary temperatures it does 
not react appreciably with oxygen and does not tarnish 
greatly in the air. It is ductile and malleable and easily 
made into thin foil. While it is below magnesium in the 
electromotive series of metals, it is strongly positive. 
It decomposes concentrated hydrochloric acid vigor- 
ously, with the evolution of Irydrogen. With nitric acid 
the action is practically nil; with sulphuric acid there is 




Fig. 66. — Thermit crucible, sectional view. 

practically no action at room temperature, but when 
heated to boiling the metal is oxidized and sulphur di- 
oxide evolved as is usual in such cases. Strong alkaline 
solutions attack aluminum readily and form a class 
of salts called alaminates, corresponding to the zineates, 
mentioned previously. 

6. Uses. — On account of its electric conductivity it is 
used in some localities as feed wires for trolley systems. 
In the home it makes an ideal cooking vessel. Its con- 
ductivity is about the equal of copper, so that all por- 
tions of the vessel become heated alike and food prod- 
ucts which burn easily are much less readily scorched 



396 APPLIED CHEMISTRY 

than in ordinary granite ware or tinware. Further, it 
is not attacked by weak acids such as those found in 
any fruits used as food. Moreover, it is light, does not 
tarnish readily, and is easily cleaned. Anything alkaline 




Fig. 67. — A thermit crucible ready for use in mending a broken casting. 
(By courtesy of the Goldschmidt Thermit Co.) 

in character cannot be cooked in aluminum vessels but 
none of our food is alkaline. In the finely powdered 
form aluminum is mixed with linseed oil and used as a 
paint for metallic objects to which it adheres well. Its 
use in this way is seen in many of the penny-weighing 



THE ALUMINUM FAMILY 



397 



machines, mail boxes, steam and hot water radiators, 
and other familiar objects. Very considerable quanti- 
ties of powdered aluminum are used in a patented arti- 
cle called "thermit." This consists of ferric oxide and 




Fig. 68. — A thermit crucible in operation, mending a broken casting 
courtesy of the Goldschmidt Thermit Co.) 



(By 



aluminum intimately mixed ; for use it is put into a cru- 
cible of suitable size, conical in shape, as shown in Fig. 
66, and a small amount of powdered magnesium placed 
on top as kindling. When everything is ready the mag- 
nesium is lighted. The heat thus obtained is sufficient 



398 APPLIED CHEMISTRY 

to start the chemical action between the aluminum and 
ferric oxide, Fe 2 3 . Once begun it is self continuous 
from the heat liberated. In a short time the aluminum 
has become aluminum oxide and the iron is free, in a mol- 
ten condition with a temperature over 1,500°. In fact, 
it is said that a temperature of 3,000° is often reached 
in the process. By substituting the oxides of other 
metals, such as chromium or vanadium or manganese, it 
is possible to obtain these rare metals in a pure condition. 
The process is used for welding almost everything of 
any size, made of iron or steel. Thus are mended broken 
drive wheels for locomotives, propeller shafts for great 
engines, rails in street railway systems, and the like. 
It is frequently used on shipboard for repairs not easily 
made otherwise. The aluminum oxide obtained as a by- 
product, is often used for the manufacture of synthetic 
rubies and sapphires already mentioned and as an abra- 
sive. Another extensive use for aluminum is in the man- 
ufacture of steel. There is a tendency for molten steel, 
made as much of it is, to retain oxygen or other gases 
within the mass. This is probably due to the viscosity. 
When such ingots of steel are made into rails these "air 
holes" form weak places and^probably are occasionally 
the cause of railway accidents. On account of the ten- 
dency of aluminum to combine with oxygen readily 
at high temperatures, a certain amount of the metal is 
added to the steel: the aluminum combines with the oxy- 
gen, forms a kind of slag and rises to the to]). 

7. Alloys. — Aluminum forms several alloys of value. 
Magnalium, containing about 2 per cent of magnesium, 
has already been mentioned. (See p. 381.) Aluminum 
bronze is prepared in two varieties, one with a very 
small percentage of copper, which is even whiter than 
pure aluminum and resembles silver closely except in 



THE ALUMINUM FAMILY 399 

density. It is used extensively in novelty articles and 
occasionally in such kitchen utensils as teapots. The 
other variety, with copper as high as 90 per cent, some- 
what resembles gold in color and is frequently used in 
making watch cases as well as a great variety of novelty 
articles. 

8. Alums. — An alum is a double sulphate of -a univalent 
and a trivalent metal. There are many of them, but 
the most common is potassium aluminum sulphate, 
K 2 S0 4 .A1 2 (S0 4 ) 3 .24H 2 0. Almost as common is ammo- 
nium alum in which ammonium has taken the place of the 
potassium in common alum. Sodium being univalent, en- 
ters into the composition of several alums; chromium 
and trivalent iron, likewise, may take the place of alu- 
minum in common alum. They are all hydrates and con- 
tain the same amount of water; they are all also iso- 
morphous, that is, they all crystallize in the same shape. 
"Burnt" alum is obtained by heating alum to expel the 
water of combination. It is a mild caustic and is some- 
times used medicinally in that way, especially for ulcer- 
ations of the mouth. 

9. Uses of Alum. — Mention has already been made that 
alum is used as a coagulant in purifying muddy waters 
for city supplies. More often, not alum, but aluminum 
sulphate is used, although it is generally referred to as 
alum. Its reaction with the milk of lime is 

3Ca(HO) 2 + A1 2 (S0 4 ) 3 -^ Al 2 (HO) 6 + 3CaS0 4 . 
Likewise, alum has been spoken of as an ingredient of 
baking powders. More often, here also, aluminum sul- 
phate is used instead of real alum. It is supplied the 
baking powder factories under the trade name of C.T.S. 
meaning "cream tartar substitute." The chemical action 
has already been noted on page 329. 

10. Aluminum Hydroxide, Al._,(HO),.. — This is easily 



400 APPLIED CHEMISTRY 

prepared in the laboratory by treating a solution of 
alum with ammonium or sodium hydroxide, taking care 
not to use the latter reagent in excess. Sodium carbon- 
ate may be substituted for the alkali. It is a white 
gelatinous precipitate, in many ways a very interesting 
compound chemically. Like zinc hydroxide, it ionizes 
both as a base and as an acid, thus. 

Al(HO) 3 ^Al+ (HO), (HO), (HO), 

H 3 A10 3 & H, H, H + AIO3. 

As a result aluminum hydroxide is very soluble not only 
in acids, with which it forms aluminum salts with alu- 
minum as the positive ion, but is also soluble in bases, 
with which it forms aluminates, in which the negative ion 
is -AIO3. To illustrate, 

Al(HO) 3 + 3HC1 -> A1C1 3 + 3H 2 0, 
H 3 A10 3 + 3NaHO -4 Na 3 A10 3 + 3H 2 0. 

Its position in the table, near the acid forming elements, 
would lead us to expect such behavior. 

On account of its gelatinous character not only has it 
the power of clarifying muddy waters, but also of remov- 
ing colors from solutions. Thus, if an alum solution, 
deeply colored with some dye, such as carmine, has a 
little alkali added to precipitate the aluminum as hydrox- 
ide, in settling, the aluminum hydroxide will carry with 
it practically all the coloring matter. Such precipitates 
dried and ground in oil are sold as tube paints for artists 
under the name of lakes, of crimson and other brilliant 
colors. It is the same principle that makes it a good mor- 
dant. Precipitated within the fibers of the cloth it holds 
or fixes the color. Canvas for tents and other fabrics 
are sometimes waterproofed by this compound. Treated 
first with aluminum chloride or some similar compound 



THE ALUMINUM FAMILY 401 

the cloth is heated by steam which hydrolyzes the alu- 
minum compound, forming aluminum hydroxide within 
fibers of the cloth. Upon drying it becomes waterproof. 
Some papers are sized by aluminum hydroxide. To the 
pulp aluminum sulphate and rosin soap are added; 
through hydrolysis aluminum hydroxide is precipitated 
in the pulp. When dry it is run between hot rollers. 
This melts the rosin and gives a surface to the paper while 
the aluminum hydroxide fills the pores, so that ink is not 
taken up readily. 

Exercises for Review 

1. Name the members of the aluminum family and give location 
in the table. 

2. State what is true of the abundance of aluminum. Name 
some familiar natural compounds. 

3. What is emery? The ruby? Kaolin? A synthetic stone? 

4. Describe the preparation of aluminum. What is a flux? 

5. Give the characteristics of aluminum. 

6. Why is aluminum suited for cooking vessels? What advan- 
tage has it over copper? 

7. Describe the use of thermit. 

8. Name some alloys of aluminum and give uses. 

9. What is an alum? Name two. What is burnt alum? 

10. What is the meaning of the term isomorphous? 

11. Why is aluminum hydroxide soluble in both acids and bases? 
What other hydroxide has been seen to have the same property? 

12. How are painters' lakes made? 

13. What is meant by sizing paper? 

14. Complete the following equations, 

A1 2 (S0 4 ) 3 + KHO —> , 
AL,(HO) (i + H 2 S0 4 -^ , 
AL_(HO) 6 (heated) -^ , 
A1 2 3 (electrolyzed) — > , 
Fe 2 3 + Al — » , 
Al + 2 -> . 

Note. — The student will use the amounts as needed in the above 
equations. 



CHAPTER XXXIII 
THE LEAD FAMILY 



Outline — 

Members of the Group 
Tin 

(a) Occurrence 

( b ) Characteristics 

(c) Uses 

(d) Alloys 

(e) Compounds 
Lead 

(a) Occurrence 

(b) Characteristics 
(<") Uses 

(d) Alloys 

(e) Compounds 

(a) The Oxides 

(b) Lead Acetate 

(c) White Lead 

(d) Chrome Yellow 
Storage Batteries 

1. Metals of the Group. — The only common metals be- 
longing* to this group are tin and lead, the former with 
an atomic weight of 119 and the latter, 207.1. Their 
position in the table should show a valence of fonr and 
their higher oxides indicate this. 

2. Occurrence of Tin. — The oldest tin mines of the 
world are those of Cornwall, England. It is said that 
the ancient Phoenicians obtained their supplies from 
this source. These mines now at great depth and ex- 
tending out under the ocean are still in operation but 
produce scarcely 10 per cent of the world's output of 
the present time. Most of that used comes from the 

402 



THE LEAD FAMILY 403 

East Indies where it is found as tin oxide, Sn0 2 , called 
cassiterite. It is the same ore as that from the English 
mines. 

3. Characteristics. — Tin is a white metal with a melt- 
ing point of 232° C. It is soft, very malleable and has a 
specific gravity of 7.3. It is crystalline in structure, 
but much less so than antimony or bismuth. Like phos- 
phorus, sulphur and some other elements already stud- 
ied, tin also occurs in an allotropic form not often seen. 
Kept continuously below 20° C. it sometimes changes to 
a gray powder, expanding to such an extent that its 
specific gravity is only 5.8. Tin is not tarnished in the 
air or attacked by any of the organic acids. It decom- 
poses hydrochloric acid with the evolution of hydrogen, 
also concentrated nitric, with the formation of nitrogen 
peroxide. Hot sulphuric acid gives off with tin sulphur 
dioxide, as is usual in such cases. 

4. Uses of Tin. — Because of its permanence in the 
air tin is used extensively in protecting iron in what 
is called "tin plate." It is made in a manner similar 
to that used for galvanizing iron. Clean, heated sheets 
of steel are dipped into molten tin and upon removal a 
coating adheres. However, as iron is more electroposi- 
tive than tin, if the coating is scratched so as to expose 
the iron the corrosion is then rapid. The reverse is true 
with galvanized iron. Of tin plate are made the so-called 
"tin cans" used so extensively in preserving various 
food products. During the year 1919 more than six bil- 
lion tin cans were used in the United States in the 
various canned-food industries. In the infancy of food 
preservation in this manner, each canner made in his 
own establishment by hand labor the cans needed. A 
good workman could not produce over 150 per day; 
now bv machine they are turned out at the rate of about 



404 APPLIED CHEMISTRY 

one per second. Heavy tin plate is used for roofing 
and gutters. Some years ago cooking vessels of tin 
plate were common, but they have been largely replaced 
by granite ware, which is more serviceable, and more 
recently by aluminum. Copper cooking vessels used in 
large eating houses, such as the Harvey system, are 
tinned on the inside to prevent attack by organic acids. 
This has to be done somewhat frequently, but the proc- 
ess is simple. The vessel is thoroughly cleaned as if 
for soldering, is heated to the melting point of tin and 
then the powdered metal rubbed on the surface to which 
it adheres. The flux used in cleaning the copper, usu- 
ally ammonium chloride, prevents oxidation when the ves- 
sel is heated. Common brass pins usually have a thin 
coating of tin to prevent their tarnishing in the air. 

5. Alloys. — Many valuable alloys of tin are used in 
the arts. Bronze is composed of copper and tin, some- 
times with zinc added ; brittania and pewter have al- 
ready been mentioned, as have certain fusible alloys. 
(See p. 289.) 

Soft solder contains tin and lead in equal proportions. 
Tin is also an important component of the most common 
dental amalgams. 

6. Compounds. — Tin forms both stannous and stannic 
salts, represented by the chlorides, SnCl 2 and SnCl 4 . The 
stannous chloride is an unsaturated compound and 
therefore a reducing agent. Added to a solution of 
mercuric chloride, first a white precipitate of calomel 
is obtained ; upon warming or adding more stannous 
chloride a gray or black precipitate is formed consisting 
of finely divided mercury or a mixture of it with mer- 
curous chloride. These two equations represent the re- 
actions occurring, 



THE LEAD FAMILY 405 

2HgCl 2 + SnCl 2 -> SnCl 4 + Hg 2 Cl 2 , 
Hg 2 Cl 2 + SnCl 2 -> SnCl 4 + 2Hg. 

The experiment serves as a test for mercuric compounds, 
or reversed, for a stannous salt. On account of this 
reducing power of stannous chloride it is used with 
gold chloride in toning printing out papers as already 
described. 

There are two oxides of tin, stannous, SnO, and stan- 
nic, Sn0 2 . The latter is the compound found native. 
It may be obtained by treating tin with concentrated 
nitric acid and heating the white powder obtained. It 
is white when cold, but distinctly yellow when hot. 
Stannic acid, which is a white gelatinous compound, 
is used extensively in weighting silk goods. The chlo- 
rides are used somewhat as mordants. 

7. Occurrence of Lead. — Galena, PbS, is the only im- 
portant ore of lead. It is a lustrous, dark gray mineral 
crystallizing in cubes, with cubical lines of cleavage. 
It is associated with many of the zinc deposits in south- 
west Missouri and with silver and other metals in many 
of the Western States. 

8. Characteristics of Lead. — Lead is a dark gray metal 
with a specific gravity of 11.38 ; it is soft and malleable 
but of little tenacity. It tarnishes somewhat readily 
in the air, but the coating adheres firmly and serves 
to protect the metal from further oxidation. The melt- 
ing point is 325° C. Being just above hydrogen in the elec- 
tromotive series it has little power of replacing that 
element in acids. With nitric acid it reacts as do most 
of the metals to form nitric oxide, thus, 

3Pb + 8HNO3 -* 3Pb(N0 3 ) 2 + 4H 2 + 2NO. 

Sulphuric acid, boiling hot and much concentrated pro- 
duces sulphur dioxide, thus, 



406 APPLIED CHEMISTRY 

Pb - 2H 2 S0 4 -> PbS0 4 - 2H 2 - S0 2 . 

Acetic acid, though a weak organic acid, reacts slowly 
with lead, forming the acetate. Lead salts are all poi- 
sonous and are difficult of elimination from the system, 
hence are what are called accumulative poisons. 

10. Uses. — Lead is used largely for making pipe. Mol- 
ten lead near the point of solidification is forced by hy- 
draulic pressure through annular openings. It is used 
as waste pipes in plumbing, and for protecting over- 
head and underground electric cables. In sheet form 
lead is used to line the rooms where chamber sulphuric 
acid is manufactured, also for sinks in chemical laborato- 
ries and other places where acids are used. Many of 
its alloys are valuable. Common solder has been men- 
tioned as has also type metal, containing lead, antimony 
and tin. It will also be recalled that shot is an alloy 
of lead and arsenic. Alloyed with antimony it is used 
extensively in making storage batteries. 

11. The Oxides. — Three oxides of lead are common, 
the monoxide, PbO, often called litharge; lead dioxide. 
PbOo ; and minium, Pb 3 4 , often called reel lead. The 
first is of light brown color, the second dark brown 
and the third red. All are in the form of powders. 
Litharge is a by-product of the silver refineries and is 
used largely in the manufacture of flint glass. (See p. 
300.) Red lead is used in making gas-tight joints in 
plumbing, also as a red paint for metals. The dioxide is 
used in storage batteries. 

12. Lead Acetate, Pb(C 2 H 3 2 ) 2 .3H 2 0.— Commercially 
this is known as sugar of lead because of its sweet taste. 
It is easiest made by treating lead monoxide with acetic- 
acid, thus, 

PbO-2HC 2 H 3 2 -» H 2 0-Pb(C 2 H 3 2 ) 2 . 



THE LEAD FAMILY 407 

It is a white crystalline salt, readily soluble in water. 
It is often used in solution as an external application 
in cases of "ivy poisoning;." 

13. White Lead. — Chemically, white lead is basic lead 
carbonate, Pb(HO) 2 .2PbC0 3 . It is the most commonly 
used white paint. It was formerly made entirely by 
what was known as the "old Dutch process" which re- 
quired several weeks for its completion. It consisted 
in the exposure of "buckles" or short strips of sheet 
lead to the fumes of strong vinegar or acetic acid, and 
the introduction of carbon dioxide. This gas was ob- 
tained from tan bark which was used to cover the pots 
containing the lead and acid. The heat needed was 
obtained by the decomposition of refuse from stables 
with which the pile of pots was covered. At the pres- 
ent time most of the commercial supply is manufac- 
tured by a more rapid process. By means of compressed 
air with an apparatus on the order of an atomizer, the 
molten lead is made into a fine dust. This is treated 
with acetic acid, and owing to the finely divided condi- 
tion of the lead, the process is completed in a few days. 
Carbon dioxide is then introduced or sodium carbonate 
added, which produces the basic carbonate. It is dried 
and ground in linseed oil. White lead as a paint has one 
disadvantage in sections where much soft coal is used. 
Considerable quantities of hydrogen sulphide are pro- 
duced. This gas reacts with the lead compounds form- 
ing the sulphide, PbS, which is black. The paint as a 
result becomes grayish in color. The following equation 
will illustrate the interchange, 

PbC0 3 + H 2 S -» PbS + H 2 + C0 2 . 

Zinc white, the other common white paint, when thus 
treated does not change in color, for the reason that 



408 



APPLIED CHEMISTRY 



zinc sulphide is a pure white compound, ZnO + H 2 S — > 
H 2 + ZnS. 

14. Lead Chromate, PbCr0 4 . — Commercially known as 
chrome yellow, lead chromate is probably the best yellow 
pigment to be had. It is prepared by treating lead ace- 
tate in solution with potassium chromate or dichromate. 
Lead chromate is insoluble in water, hence forms a pre- 
cipitate. It is filtered out, washed, and dried. For use 
it is ground in oil. 

15. Other Compounds. — The chloride, PbCl 2 , nitrate, 
Pb(N0 3 ) 2 , and sulphate, PbS0 4 , are three well-known 
compounds, but they have few practical uses and need 



Fig. 69. — A battery "grid. 



not be considered here. Lead iodide, dissolved in boil- 
ing water and allowed to cool, crystallizes out again 
in beautiful golden scales. 

16. Storage Batteries. — In this day of motor cars a 
study of lead would hardly be complete without some- 
thing about storage batteries. Each cell of a storage 
battery consists of a number of lead plates or " grids" 
separated from each other by thin sheets of wood. One 
set of these grids is connected to the positive post or 
pole and the other alternating set to the negative post. 
The wood serves to keep them from touching each other 
yet does not prevent the passage of the ions from one 
plate to another. These grids are not solid sheets of 



THE LEAD FAMILY 409 

lead but mere skeletons like the registers over hot-air 
furnace pipes as shown in Fig. 69. One set is packed 
tightly with lead dioxide or with red lead or both mixed: 
the other set with finely divided lead. They are then 
placed in a container with dilute sulphuric acid as the 
electrolyte. In charging the battery a current is led 
in from a dynamo during which time the lead dioxide 
is the anode. To this the sulphate ions will be attracted, 
which in combining with the lead oxide will give up their 
negative charge and convert a portion of the oxide into 
sulphate. The hydrogen ions of the sulphuric acid will 
move to the cathode, and, giving up their charge, the 
hydrogen escapes, leaving the lead plate positively 
charged. Two to three days are needed in bringing the 
battery up to the desired strength. When put into serv- 
ice, what was the negative pole or cathode now be- 
comes the positive pole. The reverse process now takes 
place; the lead is slowly converted into sulphate as 
it loses its positive charge and the sulphated oxide at the 
other pole is slowly reduced to oxide again by the hy- 
drogen ions which move in that direction. 

Exercises for Review 

1. Name the metals of the lead group. Look up the table and 
see if any other elements belong in the same family. 

2. What can you say of the occurrence of tin? What is the 
name of the only ore? 

3. Describe tin. Under what conditions may the amorphous va- 
riety form? 

4. What is tin plate? Give some of the uses for tin plate. 

5. Give some other uses for tin. Name its more important alloys. 

6. What two classes of compounds does tin form? Why is stan- 
nous chloride a reducing agent? 

7. Name the oxides of tin and give formulas. 

8. W r hat is the chief ore of lead? Where found in the United 
States? 



410 APPLIED CHEMISTRY 

9. Describe lead. Where is it in the electromotive series? What 
does this tell one about the reaction of a metal with an acid? 

10. Give the more important uses of lead. 

11. How is lead pipe used? How made? 

12. Name three oxides of lead and give formulas. 

13. How is sugar of lead made? Write equation. 

14. What is Avhite lead? How formerly made? How made at 
present ? 

15. What is chrome yellow? What is its use? 

16. Describe the construction of a storage battery. 

17. What is an electrolyte? What is the electrolyte in a stor- 
age battery? 

18. Why do instructions in regard to care of storage batteries 
tell one not to bring a lighted match near? 

19. If the water in the battery did not evaporate at all, would 
it still be necessary to add distilled water occasionally? Explain 
your answer. 

20. Complete the following equations using amounts as may be 
needed, 

PbCl, + H 2 S0 4 -* , 
Pb(N0 3 ) 2 + KI -» , 
Pb + H,S0 4 -^ , 
PbOL, + K 2 Cr0 4 —> , 
PbO + HN0 3 -^ , 
Pb + HN0 3 -> , 
PbS -f O, ~* . 



CHAPTER XXXIV 

THE CHROMIUM FAMILY 
Outline — 

Members of the Group 
Chromium 

(a) Preparation 

( b ) Characteristics 

(c) Uses 

(d) Compounds 

(a) Chromates 

(?>) Bichromates 

(c) Chromic Salts 
Tungsten 
Uranium 

1. Members of the Group. — To this group belong 
chromium, molybdenum, tungsten and uranium, all of 
them rather unfamiliar elements. Their higher oxides 
all show a valence of six as would be expected from 
their position in the table. Chromium has an atomic 
weight of 52, molybdenum, of 96 ; tungsten, 184 ; ura- 
nium, 238.5. 

2. Preparation of Chromium. — The easiest method of 
obtaining chromium is by the thermit process in which 
chromic oxide is substituted for the ferric oxide. This 
has been described on p. 397. 

3. Characteristics of Chromium. — Chromium is a metal 
of very high melting point, steel-gray in color and very 
hard. It does not tarnish readily in the air. With 
warm hydrochloric acid it reacts with the evolution of 
hydrogen. 

4. Uses. — The chief use of chromium is in making an 
alloy with steel which is called chrome steel. It pos- 

411 



412 APPLIED CHEMISTRY 

sesses unusual hardness and resistance to stress. It is 
used in parts of machinery as motor cars and trucks 
where great strength is required. 

5. Classes of Compounds. — Chromium forms several 
series of compounds of interest to the chemist. The 
oxide, Cr0 3 , is acidic, the anhydride of chromic acid, 
corresponding to sulphuric acid. With the metals it 
forms a number of salts called ehromates. One of the 
most common of these is potassium chromate, K 2 CrQ 4 , 
a crystalline salt of lemon-yellow color. From the ehro- 
mates by treatment with an acid, another set of salts 
is obtained, called the dichromates, of which potassium 
dichromate, K 2 Cr 2 7 , is the most common. Its formula 
might be written, K 2 Cr0 4 .O0 3 . Another oxide of chro- 
mium gives a series of salts in which chromium is the 
positive ion. Thus chromic oxide, Cr 2 3 , is a basic oxide 
with the corresponding hydroxide, Cr 2 (HO), ; , also writ- 
ten Cr(HO) 3 . Theoretically it is formed thus, 

Cr 2 3 + 3H 2 ->2Cr(HO) 3 . 

If to this acids are added Ave obtain the corresponding 
salts. Chromic compounds are mostly green or violet; 
in fact, the word chromium is from the Greek for color, 
given because so many of the compounds of this metal 
are highly colored. The following equation shows the 
preparation of the sulphate, 

2Cr(HO) 3 -f 3H 2 S0 4 ^ Cr 2 (SOJ 3 + 6H 2 0. 

6. Conversion of One Class to Another. — Very readily 
these compounds may be changed from one class into 
another. Since the dichromates contain an anhydride, 
seen when potassium dichromate is written, K 2 Cr0 4 . 
Cr0 3 , they may be regarded as acid salts. The addition 
of an alkali, therefore, should neutralize the anhydride 
and make a normal salt of it. In other words, it should 



THE CHROMIUM FAMILY 413 

become a chromate. This actually happens as shown 
by the following equation, 

K 2 Cr0 4 .Cr0 3 + 2KHO -» 2K 2 Cr0 4 + H 2 0. 

At the same time the color should change, as it does, 
from orange to lemon-yellow. On the other hand, the 
addition of an acid to the chromate converts it into 
the dichromate, thus, 

2K 2 Cr0 4 + H 2 S0 4 -> K 2 S0 4 + H 2 + K 2 Cr0 4 .CrO s . 

Chromates or dichromates treated with hydrochloric acid 
and, especially if a reducing agent be present, are 
changed into green salts with chromium as the positive 
ion, thus, 

K 2 Cr 2 7 + 14HC1 -» 2CrCl 3 + 7H 2 + 2KC1 + 3C1 2 
2K 2 Cr0 4 + 3H 2 S + 10HC1 -> 2CrCl 3 + 8H 2 + 4KC1 + 3S. 

On the other hand, compounds containing chromium as 
a positive ion may be changed to chromates by heating 
with an alkali. Oxygen is taken up from the air, thus, 

4Cr(HO) 3 + 8NaHO + 30 2 -» 4Na 2 Cr0 4 + 10H 2 O. 

7. Chromic Compounds. — Most of the chromic com- 
pounds are green in color; however, chromic alum, 
K 2 Cr 2 (S0 4 ) 4 , is violet. Chromic oxide, Cr 2 3 , is a green 
powder. It is used as a pigment, in coloring glass a 
deep green and in artificial emeralds. Chromic chloride, 
CrCl 3 .6H 2 0, may be prepared by treating chromium hy- 
droxide with hydrochloric acid. It is of a bright green 
color. Chromium sulphate, Cr 2 (SO 4 ) 3 .10H 2 O, is of a 
reddish-violet color, made by treating the hydroxide 
with sulphuric acid. 

8. Insoluble Chromates. — Potassium chromate already 
named is readily soluble in water. If to this is added a 



414 APPLIED CHEMISTRY 

solution of lead acetate an insoluble compound of lead 
ehromate precipitates out, thus, 

K 2 Cr0 4 + Pb(C 2 H 3 2 ) 2 -> PbCr0 4 + 2KC 2 H 3 2 , 

It has been mentioned already as a bright yellow pig- 
ment. Chrome red is a basic lead ehromate with the 
composition, PbO.PbCr0 4 ; it is of bright red color. Sil- 
ver ehromate, Ag 2 Cr0 4 , of deep red color and barium 
ehromate, BaCr0 4 , a pale yellow, are both insoluble 
compounds. 

9. Tungsten. — The symbol for this element is \Y. De- 
jDosits of tungsten are said to exist in both South Da- 
kota and Colorado, but most of our supply is imported. 
It is of interest mainly because of the fact that the 
filament of most electric light bulbs is now made from 
it. Such lamps give a much whiter and more brilliant 
light than the old carbon ones. For the same candle 
power tungsten lamps consume much less current and 
hence are much less expensive. AY hen first introduced 
they were very fragile and required most careful han- 
dling, hence were not received favorably by the public. 
That objection has now been removed and their life 
is practically the same as that of the carbon lamp, that 
is about 1.000 light hours. 

10. Uranium. — Uranium has the highest atomic weight 
of all the elements, 238.5. It is also remarkable in that. 
contrary to our general ideas of elementary matter, it 
has the property of disintegrating and forming other 
elements. Thus, one of the products of uranium is ra- 
dium, and from radium by a similar decomposition, he- 
lium is obtained. So, uranium forces us to the conclu- 
sion that at least some elements are capable of self dis- 
integration. 



THE CHROMIUM FAMILY 415 

Exercises for Review 

I. Name the elements of the chromium group, and give symbols. 

2. What is the simplest method of obtaining pure chromium? 

3. Give chief properties of chromium. 

4. For what is chromium used? 

5. Name three classes of chromium compounds and give one ex- 
ample of each. 

6. Name two oxides of chromium with formulas. Which one is 
acidic? Of what acid is it the anhydride? 

7. Why will an alkali change a dichromate into a chromate? 
1 llustrate. 

8. Show how chromates may be changed into dichromates. 

9. How may chromates or dichromates be changed into chromic 
salts? 

10. Name three chromic salts and give formulas. 

II. Name four insoluble chromates and give formulas; also 
uses, if any. 

12. What use has tungsten? Why are such lamps desirable? 

13. What is the most remarkable property of uranium? 

11. Complete the following equations, using amounts needed to 
balance, 

Cr(HO) 3 + HOI -> , 
Cr(HO) 3 + H 2 S0 4 -» , 
Or 2 3 + H 2 S0 4 — > , 
Or0 3 + H.,0 -> , 
Cr,0 3 + H 2 -> , 
E^CrO, + AgN0 3 -> , 
K 2 Cr0 4 + BaCl 2 -* , 
PbCl 2 + K 2 Cr0 4 -> . 

15. In Section 6, remembering that reduction consists in lower- 
ing the valence of an element and oxidation is the reverse, raising 
the valence, has chromium been oxidized or reduced in the last 
three equations given? 

16. In the first two equations in Section 6, has chromium been 
oxidized or reduced? Give reason for vour answer. 



CHAPTER XXXV 

MANGANESE AND COMPOUNDS 

Outline — 

Manganese 

Relation to Other Elements in the Table 

Characteristics 

Compounds 

(a) The Oxides 

(b) Manganic Compounds 

(c) Manganates 

(d) Permanganates 

1. Position in Periodic Table. — Manganese is found 
in the same column in the table as the halogen group, 
but at the left hand side of the space. The correspond- 
ing positions in the long periods that follow manganese, 
by looking at the table are seen to be vacant. So at 
present this element is all alone. 

2. Characteristics. — In some respects manganese re- 
sembles iron. It occurs in nature as a dioxide, Mn0 2 , 
called pyrolusite, always mixed with iron. It is a gray- 
ish metal, with the power of reacting with dilute acids 
and evolving hydrogen. It forms an alloy with iron and 
is tarnished when exposed to the air. Its chief use is in 
making manganese steel, by alloying it with iron. 

3. The Oxides. — Manganese forms five oxides most of 
which are of no great importance. The lowest is MnO, 
which is a basic oxide ; as they increase in amount of 
oxygen, as might be expected, they become more acidic 
until the highest is reached, Mn 2 7 , which is strongly 
acidic. The dioxide is the most familiar to the student 
because he has used it on several occasions. The hep- 

416 



MANGANESE AND COMPOUNDS 417 

toxide shows the metal to have the combining power 
or valence of seven as would be expected from its posi- 
tion in the table. We have used the dioxide catalyti- 
cally in making oxygen, and as an oxidizing agent in 
the preparation of bromine and chlorine. It is a basic 
oxide and unites readily with acids to form manganous 
salts. 

4. Manganous Salts. — Manganese forms both mangan- 
ous and manganic salts just as chromium does, but the 
manganous are the more common. They may be ob- 
tained from manganese dioxide by treatment with an 
acid. Thus manganese dioxide with hydrochloric acid 
gives the chloride, 

Mn0 2 + 4HC1 -> MnCl 2 + 2H 2 + Cl 2 . 

On evaporation the solution gives a pink crystalline hy- 
drate, with the formula, MnCl 2 .4H 2 0. The sulphate may 
be obtained by treating the dioxide with sulphuric acid, 
thus, 

2Mn0 2 + 2H 2 S0 4 -> 2MnS0 4 + 2H 2 + 2 . 

It is also a pink hydrate, but the quantity of water 
varies at different temperatures. At ordinary condi- 
tions the formula is MnS0 4 .5H 2 0. Manganous salts 
or the dioxide, fused with borax, impart an amethyst 
color to the bead. 

5. Manganates and Permanganates. — Manganese forms 
a series of salts known as manganates, of which 
potassium manganate, K 2 Mn0 4 , is one of the more com- 
mon. The permanganate, KMn0 4 , is a much more im- 
portant compound. It is a purple solid with greenish 
luster, and crystallizes in small rhombic prisms. In 
solution it gives a deep purple color. It has frequent 
use in the chemical laboratory in estimating the quantity 



418 APPLIED CHEMISTRY 

of iron and in various other ways. It is sometimes nsed 
in cisterns for oxidizing the organic impurities present. 

Exercises for Review 

1. Give the location of manganese in the table. 

2. How does the element occur in nature? 

3. Give the chief properties of manganese. 

4. What is the chief use of manganese? 

5. How many oxides of manganese are there? Name two and 
state whether basic or acidic. 

6. Describe the appearance of manganese dioxide. What uses 
has it? 

7. How may manganous chloride be made? Describe it. 

8. Describe potassium permanganate. Give its uses. 

9. Complete these equations, using such amounts as are neces- 
sary, 

Mn0 2 + HBr -» , 
MnO, + HC1 -> , 
Mn 2 7 + H 2 -> , 
Mn(HO), + H 2 S0 4 -> , 
MnCl, + KHO -> , 
MnS0 4 + Ca(HO) 2 -» . 

10. In the following equations, what substances have been re- 
duced and what oxidized? 

Mn0 2 + 4HC1 -4 MnCl 2 + 2H 2 + -CL, 

2KMn0 4 + 8IL,S0 4 f lOFeSO, -> 5Fe 2 (0 4 ) 3 + K 2 S0 4 + 2MnS0 4 4 
8H 2 0. 



CHAPTER XXXVI 
THE IRON GROUP 



Line- 




Members of the Group 


Iron 




(«) 


Occurrence 


0) 


Eeduction of 


(o) 


The Blast Furnace 


(d) Wrought Iron 


(e) 


Steel 




(a) Cementation Process 




(b) Bessemer Process 




(c) Open Hearth Process 




(d) Characteristics 




(e) Method of Tempering 




(/) Varieties of 




General Characteristics of Iron 




Compounds 




(a) Ferrous Sulphate 




(b) Ferric Chloride 




Oxidation and Reduction of Salts 




Pigments 


Nickel 




(a) 


Characteristics 


(*) 


Uses 


(o) 


Compounds 


Cobalt 




(a) 


Characteristics 


(fe) Compounds 



1. Members of the Group. — Iron, nickel and cobalt are 
usually associated, but not as a periodic group. They 
have atomic weights close together and do not form a 
vertical column in the table. Tavo of them are elements 
of importance, iron being intrinsically the most valuable 
of all metals. 

419 



420 APPLIED CHEMISTRY 

2. Occurrence of Iron. — There are several ores of 
iron used in the preparation of the metal. Of these, 
hematite, Fe 2 3 , is the most important. It is a dark 
colored mineral, reddish-brown to black, which drawn 
across a piece of unglazed porcelain gives a dull red 
streak. It is this fact that gave the name to the ore. 
the word hematite being from the Greek meaning Mood. 
Limonite, which is a hydrated oxide, Fe 2 3 .3H 2 0, gives 
a yellow streak, and received its name frcm the Latin 
word for lemon. In some sections, the magnetic oxide. 
Fe 3 4 , is found. The carbonate, FeC0 3 , called siderite, 
and the disulphide, FeS 2 , commonly known as "fool's 
gold" should also be mentioned. Iron never occurs free 
upon the earth except in very minute quantities. Meteo- 
rites have been discovered containing from 92 to 97 per 
cent of iron and the remainder nickel. Lieutenant Peary, 
some years ago, in one of his Arctic trips discovered 
through the aid of his Esquimos two large meteorites, 
one of which weighed in the neighborhood of 100 tons, 
the largest ever found. Later, he brought this one back 
to the Brooklyn Navy Yards. In the form of compounds, 
iron is found everywhere. It is the most common coloring 
agent in rocks and soils, and exists in many food prod- 
ucts and in the blood. 

3. Reduction of Iron. — It will be remembered that 
zinc is reduced from its chief ore by means of coke, 
after the preliminary roasting has converted the sulphide 
into an oxide. Since most of the iron ores are already 
oxides, this preliminary treatment is not necessary. 
Coke is used to furnish the heat and the carbon for the 
reduction. 

4. The Blast Furnace. — The ordinary blast furnace 
varies from 20 to 25 feet in diameter and from 75 to 
90 feet in height. It is made of fire brick and strength- 



THE IRON GROUP 



421 



enecl on the outside by heavy boiler plate iron. The top 
of the furnace is so constructed that it is practically air- 
tight, and any gases formed within must pass off 
through a pipe near the top shown in Fig. 70. How- 
ever, as the process is a continuous one, additions of 




Fig. 70. — A blast furnace for 



422 APPLIED CHEMISTRY 

material are made repeatedly through a hopper which 
opens mechanically when a load is dumped upon it and 
then closes again when the material has fallen into the 
furnace. Near the bottom is an opening for drawing 
off the molten iron, which is kept closed by means of 
clay until needed. At some distance above is an open- 
ing for the exit of the slag. As the quantity is usually 
large, this is open most of the time with a steady outflow 
of the molten material. Above this, entering from the 
sides, are the blast pipes, often called tuyeres, through 
which the air is forced into the furnace. This is needed 
to give the intense heat required. The furnace is tapped 
usually every twelve hours and the molten iron run off 
into trenches and side trenches in the ground. These 
short trenches are called "pigs" and the iron formed in 
them "pig iron." Sometimes the molten iron is run into 
steel molds bolted upon an endless chain, which moves 
slowly forward as each is filled from a large cauldron. 
(See Fig. 71 for illustration of method of molding pig 
iron.) 

5. The Charge. — The materials used in the "charge" 
put into the furnace are usually iron ore, coke and lime- 
stone. Most ores when brought from the mine contain 
more or less silica. In the furnace the limestone with 
the silica forms a species of glass, called slag. It floats 
above the molten metal and protects it from the oxidizing 
action of the blasts of air. When the ore contains lime- 
stone as a gang ue, instead of silica, some silicious material 
is added to serve as the flux. 

6. The Chemical Action. — Owing to the large amount 
of air introduced through the tuyeres, at the bottom of 
the furnace carbon dioxide is produced. (See p. 169.) 
As this flows upward it meets red-hot carbon and is 
changed to carbon monoxide, thus, 



THE IRON GROUP 

CO. + C -> 2CO. 



423 



This being an unsaturated gas removes the oxygen from 
the iron ore and the free iron thus produced flows to 
the bottom of the furnace. The gas, which escapes at 
the top, contains much carbon monoxide as well as other 
combustible gases. This is used to heat the air forced 




Fig. 71. — A blast furnace, showi 



for the ' pigs 



424 APPLIED CHEMISTRY 

in and to run the fans for the air pressure. The iron 
thus obtained, is known as cast iron. It contains a high 
percentage of carbon, sometimes as much as 3 or 4 per 
cent as well as silica and other impurities. It is coarse 
grained, brittle, hard, and has a melting point relatively 
low, about 1250° C. 

7. Wrought Iron. — Wrought iron is made by heating 
the cast iron in a reverberatory furnace with ferric 
oxide. The purpose of the oxide is to furnish oxygen 
for union with the carbon in the iron, by which carbon 
monoxide is formed. These are sometimes called pud- 
dling furnaces, because the molten pig iron is "puddled'' 
or stirred so as to facilitate the action. When the mass 
has become stiff and very difficult to stir, it is known that 
the carbon is burned out. Pure iron melts with much 
more difficulty than impure, and the temperature of these 
furnaces is only sufficient to keep the impure form in a 
molten condition. It is the same principle, seen often 
before, in which a solution will remain liquid while the 
solvent will solidify. At this stage the iron, called 
"bloom," is removed from the furnace, and beaten with 
trip hammers, which forces out the silica and any slag 
remaining. Such is now wrought iron. It is malleable 
and may be welded ; it is fine grained, somewhat more 
dense than cast iron, melts at about 1,500° C. and contains 
only about 0.1 to 0.2 per cent of carbon. It should not 
contain much phosphorus or sulphur. Wrought iron is 
made into sheets, and is used in chains, wire, and in 
many other ways where a cheap, malleable metal is de- 
sired. 

8. Steel. — The oldest method of making steel was by 
the cementation process. Bars of wrought iron were im- 
bedded in powdered charcoal and heated strongly for a 
number of days. The iron slowly absorbed small portions 



THE IRON GROUP 



425 



of the carbon and was changed thereby into steel. How- 
ever, it was far from satisfactory, for the reason that the 
carbon was not taken up uniformly. Some portions would 
contain so much as to be more or less brittle, while others 
would not contain enough. Cast steel was first made by 
melting cementation steel and molding it into a bar so as 
to give uniform composition. This greatly improved the 
produce previously obtained. The process is entirely too 
slow for modern demands; for years, until recently, most 
of the steel used has been made by the Bessemer process 




Fig. 72. — The Bessemer converter. 



(Fig. 72). This process uses a movable furnace, called 
a converter, made of boiler-plate iron and lined with a 
silicious earth called ganister, which is infusible. The 
compressed air passes up through a supporting post, 
through the horizontal trunnion, and down the pipe into 
the tuyere box or air chamber, then into the body of the 
converter. For use it is filled half or two-thirds with 
molten cast iron and the air is turned on. No heat is ap- 
plied ; the interaction of the oxygen of the air with the car- 
bon and other impurities in the iron is sufficient not only 
to keep the metal molten, but even raise the temperature. 



426 APPLIED CHEMISTRY 

At first luminous flames and great showers of sparks shoot 
from the mouth of the converter, but as the carbon is 
burned out the action becomes more quiet until finally 
it practically ceases altogether. If the product obtained 
at this stage were hammered, it would form wrought iron. 
For steel a definite amount of spiegel iron is added. This 
is an iron-manganese alloy which may have as high as 
20 per cent of manganese, but usually only a small pro- 
portion. It contains also a fixed amount of carbon so 
that any required proportion of carbon may be thus put 
back into the iron to form the steel. The blast of air 
is continued just long enough to mix the spiegel thoroughly 
with the other when the whole is poured out and cast 
into ingots. It will be seen that the process consists in 
burning out all the carbon and then restoring whatever 
may be desired for a particular variety of steel. This 
method works successfully unless phosphorus be present 
in the cast iron. The Bessemer converter will not remove 
phosphorus, and its presence makes steel brittle. To re- 
move it, a converter lined with lime is used. Phosphorus, 
being an acidic element, unites with the lime, a basic oxide, 
forming the superphosphate of calcium, mentioned on p. 
281 as a valuable fertilizer. This modified plan is called 
the basic lining or the Thomas-Gilchrist process. 

9. Open Hearth Steel. — In the last few years much 
steel has been made by what is known as the open hearth 
or Siemens-Martin process. The cast iron, whose carbon 
content is known by chemical analysis, is mixed with a 
definite amount of hematite, ferric oxide, or some other 
iron ore, and heated in an open furnace with a gaseous 
fuel, for about ten hours. The materials are so propor- 
tioned as to leave a definite amount of carbon in the steel. 
The gas used for fuel is heated before being burned and the 



THE IRON GROUP 427 

charge is tested from time to time to know when the proc- 
ess is complete. 

10. Characteristics of Steel. — Steel is between wrought 
and cast iron in content of carbon. The amount varies 
from 0.5 to 1.5 per cent. Its most remarkable property 
is its ability to be tempered, that is, to be so treated as 
to hold a cutting edge. It also has wonderful tensile 
strength. Wires of lead, copper and steel, of equal diam- 
eter, show that steel will withstand twice what copper will 
and forty times what lead will. This is one of the chief 
reasons for the great use of steel in the arts. 

11. Tempering Steel. — If a piece of steel is heated to 
redness and then cooled slowly it is soft and malleable 
like wrought iron ; but if so heated and cooled suddenly 
it is hard and brittle. Now if it be heated again to a 
much lower temperature, ranging from 225° to 325° 
C, it assumes degrees of hardness and brittleness be- 
tween these two conditions and is suitable for cutting 
instruments. At the lower temperature, such keen- 
edged instruments as razors and instruments employed in 
surgery are made; at the higher, saws and similar tools. 
The explanation of this, put as simply as possible, is as fol- 
lows. At the temperature first used a considerable 
amount of iron carbide is formed which makes the 
steel brittle. If the bar is cooled suddenly the carbide 
remains in the steel; if cooled slowly the carbide de- 
composes and leaves less of it in the steel. At the sec- 
ond heating, if only a low temperature is used, not so 
much time is given in cooling for the iron carbide to 
be decomposed; hence, a considerable amount remains 
and the steel is harder and takes a keener edge, but is 
more brittle. When heated to a higher temperature 
more time is given for the carbide to be decomposed : 
hence, the steel is left softer, less brittle and better 



428 APPLIED CHEMISTRY 

suited for rough tools, but not capable of so keen an 
edge. 

12. Kinds of Steel. — By mixing in the converter one 
or more of some of the rarer metals, alloys of great 
value may be obtained. As they consist mainly of steel 
they are spoken of as such. Chrome steel contains a 
small percentage of chromium or sometimes both chro- 
mium and vanadium. It is a steel of special strength 
and is used in parts of machinery where great strain 
may come, as in the axles and frames of motor cars. 
Nickel steel may contain as much as 4 per cent of nickel 
and is especially desirable as armor for war vessels. It 
has great strength, is very tenacious, hard to pierce with 
projectiles, and resistant to sea water. A manganese steel 
gives a variety used for making burglar proof safes of 
very great hardness. 

13. General Characteristics of Iron. — The most im- 
portant physical properties have been given in describ- 
ing the different varieties of iron. It is well up in the 
electromotive series of metals and readily displaces hy- 
drogen from dilute acids. Very concentrated nitric acid 
products a singular condition known as the passive state 
in which it will not react with dilute acids with the evo- 
lution of hydrogen. Chromium is affected in a similar 
manner. Hammering will restore its former properties. 
In oxygen, iron when heated burns readily with a beauti- 
ful shower of sparks, and forms mainly the magnetic 
oxide, Fe 3 4 . Superheated steam, directed upon iron, 
gives it a blue color due to the formation of a closely-ad- 
hering, protecting film of this same oxide. In the air, in 
the presence of moisture, ferric oxide, Fe 2 3 , is formed; 
this being nonadhering, the metal becomes entirely cor- 
roded. 



THE IRON GROUP 429 

14. Compounds of Iron. — Iron forms two classes of 
compounds, ferrous and ferric. The former are mostly 
green in color, the latter brown. Ferrous compounds 
are unsaturated and, as a rule, tend to become oxidized 
to the ferric. 

Ferrous sulphate, FeS0 4 .7H 2 0, is commonly known 
by the name of green vitriol, or copperas. It is an 
efflorescent hydrate, but as it loses its water, it also be- 
comes oxidized from the air and forms a basic ferric 
sulphate. Therefore, unlike effloresced blue vitriol, the 
addition of water does not re-form the ferrous sulphate. 
It is used in various ways. Common black ink is a mix- 
ture of ferrous sulphate and tannic acid, which on ex- 
posure changes into a black ferric salt. To give it more 
body some mucilage is usually added and often some dye 
as well. Ferrous chloride, FeCl 2 , may be made by dis- 
solving iron in dilute hydrochloric acid. It is a very un- 
stable salt and rapidly oxidizes to a ferric. Ferrous 
hydroxide, Fe(HO) 2 may be prepared by adding, to 
any soluble ferrous salt, a solution of some alkali. If 
pure it is white in color, but as usually obtained is 
greenish, changing rapidly to brown as it is oxidized 
by the air. The double salt, ferrous ammonium sulphate, 
(NH 4 ) 2 S0 4 .FeS0 4 .6H 2 0, is the most stable of the ferrous 
salts. It is pale green in color, crystalline in structure 
and soluble in water. For experimental work in the lab- 
oratory it is far the best for use. 

15. Ferric Compounds. — Ferric chloride, FeCl 3 .6H 2 G, 
is a very deliquescent, brown solid. It is employed in 
most pharmaceutic preparations of iron. Mention has 
been made of its use in preparing the best antidote for 
arsenic. Ferric sulphate, Fe 2 (S0 4 ) 3 , may be made by the 
oxidation of ferrous sulphate with nitric acid or bro- 
mine or with some other oxidizing agent. Ferric' hy- 



■430 APPLIED CHEMISTRY 

droxide. Fe(HO) 33 may be prepared by treating ferric 
chloride with ammonium hydroxide or any other solu- 
ble hydroxide. It is a gelatinous, brownish colored 
precipitate. Heated, it loses water and becomes ferric 
oxide. Fe 2 3 . 

16. Oxidation and Reduction of Iron Compounds. — As 
stated above, ferrous salts may be readily changed to 
ferric by oxidation. If a solution of ferrous sulphate 
acidulated with sulphuric acid has nitric acid added and 
is then heated, it is changed into ferric sulphate, thus. 

2FeS0 4 + H 2 S0 4 + 2HN0 3 -> Fe 2 (S0 4 ) 3 + 2H 2 + 2N0 2 . 

Potassium permanganate is used to oxidize ferrous salts 
to ferric in the same way. As it is of a deep violet, a 
coloration of the iron solution is seen as soon as the oxi- 
dation is completed. A permanganate solution, there- 
fore, of known strength, may be used to determine the 
amount of iron present, by noting the number of cubic 
centimeters needed to oxidize a certain amount of the 
ferrous solution. The equation is 

2KMn0 4 - 8H 2 SO - 10FeSO 4 -* 

5Fe 2 (S0 4 ) 3 - K 2 S0 4 - 2MnS0 4 - 8H 2 0. 

Conversely, ferric salts may be reduced to ferrous. This 
is easily done by nascent hydrogen, thus. 

2FeCL + 2H -> 2FeCl 2 + 2HC1. 

The hydrogen may be obtained by putting pieces of zinc 
into the ferric solution and adding a dilute acid as 
hydrochloric. In a similar way hydrogen sulphide re- 
duces iron salts in the presence of an acid. thus. 

2FeCl 3 - H 2 S -h> 2FeCl 2 - 2HC1 - S. 
The sulphur is precipitated. 

17. Other Iron Compounds. — There are a few com- 
pounds in which iron forms a part of the negative ion. 
Such are potassium ferrocyanide. K 4 Fe(CN) 6 , and ferri- 



THE IRON GROUP 431 

cyanide, K 3 Fe(CN) 6 . These were formerly regarded as 
double salts as their present names indicate. Potassium 
ferrous cyanide was regarded as Fe(CN) 2 .4KCN and 
the other as Fe(CN) s .3KCN. If really double salts, as 
last written, the former would in solution contain fer- 
rous ions, and the latter ferric ions. Chemical tests show 
this is not true. Mixed with ferric or ferrous salts, they 
give compounds, one of which is known as Prussian blue, 
Fe 4 [Fe(CN) 6 ] 3 , which was formerly used frequently in- 
stead of indigo as a cheap bluing in laundry work. Both 
of the cyanide compounds have use in the laboratory in 
making delicate tests for the presence of iron. 

18. Some Pigments. — Rouge is the commercial name 
for a form of ferric oxide used in polishing. It is made 
from ferrous sulphate which is obtained in cleaning iron 
for the purpose of galvanizing. Venetian Red and other 
cheap red pigments, used for painting roofs and out- 
buildings, are largely ferric oxide mixed with more or 
less clay. Yellow ochre is a hydrated form of the same 
compound and corresponds to limonite, already men- 
tioned. It is used sometimes for priming woodwork and 
as a cheap paint. Raw and burnt sienna and raw and 
burnt umber are other well-known pigments of similar 
composition, two of them obtained, as the names indicate 
by strongly heating the oxide. 

19. Nickel, its Characteristics. — Nickel is a hard white 
metal which tarnishes very slowly in the air. It is sus- 
ceptible of a high polish. It is little attacked either 
by dilute hydrochloric or sulphuric acid. It is exten- 
sively used in plating iron. The method is the same as 
described in the case of the other metals, except a dif- 
ferent solution of nickel is used. The double sulphate 
of ! nickel and ammonium, (NHJ 2 S0 4 .NiS0 4 .l>II,0. 
gives a plating which adheres best. It is a greenish col- 
ored salt, soluble in water. Nickel is also used in coin- 



432 APPLIED CHEMISTRY 

age. alloyed with copper in the familiar five-cent piece: 
in the powdered form it is used somewhat in wireless 
telegraphy and in the familiar alloy. German silver. Its 
use in making nickel steel has been mentioned as well 
as its catalytic action in the hydrogenation of oils. 

20. Compounds of Nickel, — Niekel forms two series 
of compounds, nickelous and nickelic. The former are 
the more common. They are mostly green in color: 
however, fused in the borax bead, they give a brown 
coloration, which is distinctive. The most important 
salt is the double sulphate already mentioned as of use 
in plating. 

21. Characteristics of Cobalt, — Cobalt is a hard, white 
metal resembling nickel. It has no uses. It forms two 
classes of compounds, cobaltous and cobaltic. The for- 
mer are the more common and the more important. 
They are deep pink or reddish in color. Fused in a borax 
bead, even in minute quantity, they give a beautiful 
blue color, which serves to identify the metal. 

22. Uses of Cobalt Compounds. — Some very valuable 
pigments are made from cobalt compounds. Smalt, a 
kind of glass, made by fusing some cobalt compound as 
the oxide, with sand and potassium nitrate, is of a deep 
blue color. It is powdered and mixed in the paste used 
on the outside of iron vessels in the manufacture of 
" ' granite ware. * ' When these are heated strongly in ovens 
the coating melts and gives the familiar blue ware in 
common use. It is also ground in oil and used as a paint 
for chinaware. Several cobalt salts become blue in color 
when they lose their water of combination. Based upon 
this fact is the "cobalt barometer*' occasionally seen. It 
consists of a strip of unsized paper or cloth moistened 
with cobaltous solution. If the air is very dry the paper 
turns blue ; if damp. red. Sympathetic inks, containing 
some cobalt compound, depend upon the same property. 



THE IRON GROUP 433 

When used upon paper the pink color is scarcely visible; 
if warmed, the water of combination is removed and the 
compound turns blue. It then may be plainly read. In 
damp air it will again become invisible. 

Exercises for Review 

1. Name the metals usually associated with iron. Why do they 
not form a periodic group? 

2. Mention the chief ores of iron and give composition. 

3. How could you recognize a piece of hematite? Of limonite? 

4. Describe the construction of the blast furnace. 

5. Of what does the charge put into a blast furnace consist? 
What is the purpose of each? 

6. Describe the chemical action which takes place in the blast 
furnace. 

7. How is wrought iron made? What are some of its uses? 

8. Describe the cementation process of making steel. Why was 
cast steel used? 

9. Describe the Bessemer converter and state the principle un- 
derlying its use. 

10. What is the "Thomas-Gilchrist process of making steel? 

11. Describe the open hearth process. 

12. How is steel tempered? Explain the principle underlying. 

13. Name some different kinds of steel and state for what 
adapted. 

11. Give the chemical properties of iron. What is meant by the 
passive state? 

15. What is green vitriol? How made? Uses? Name some 
other ferrous compound. 

16. Name one ferric salt and tell how to prepare ferric hydrox- 
ide from it. What use has the hydroxide? 

17. How can ferrous sulphate be changed to ferric? Ferric 
chloride to ferrous? What is oxidation in the broad sense? 

18. Name some common iron pigments and give uses for them. 
Of what do they consist? 

19. Give the chief characteristics of nickel and uses. 

20. How is nickel plating done? 

21. Name one important compound of cobalt and give important 
use for it. 

22. What is a sympathetic ink? Explain how one made from 
cobalt compounds works. 



CHAPTER XXXVII 

THE PLATINUM AND PALLADIUM GROUPS 
Outline — 

Members of the Group 

Oceurreuce 

Platinum 

(a) Characteristics 

(6) Uses 
Osmium 
Iridium 
Palladium 

1. Members of the Group. — Osmium, iridium and plat- 
inum are associated as are iron, nickel and cobalt, but 
do not constitute a periodic group, for their weights 
run consecutively and not as octaves. Osmium has an 
atomic weight of 191, iridium, 193, and platinum, 194.8. 

2. Occurrence. — These metals are found as grains or 
small nuggets in alluvial deposits, much as is gold, but 
in very limited quantities. California produces about 
all there is obtained in the United States. Nearly the 
entire world's supply comes from the Ural Mountains in 
eastern Russia. The three metals are nearly always 
found mixed together, with platinum the more abundant. 
They are separated by difficult chemical processes which 
would not be of interest to the student. 

3. Characteristics of Platinum. — Platinum is the most 
important metal of the group. It is steel-white in color, 
very hard, not attacked by acids, but is soluble in aqua 
regia, or nascent chlorine. It is exceedingly malleable 
and ductile, and when heated may be welded like 
wrought iron. At red heat it easily forms alloys with 

434 



PLATINUM AND PALLADIUM GROUPS 435 

metals of low melting point, such as lead and antimony 
and will also combine with carbon, phosphorus and sil- 
ica. The alloys mentioned have low melting points ; 
hence, the greatest care must be exercised not to heat 
any such metals in platinum ware. If it is done, the 
alloy is readily formed, and then melts out leaving a 
hole in the platinum vessel. Silica and phosphorus ren- 
der platinum brittle, so may likewise cause serious in- 
jury. If pure, platinum has a high melting point of 
about 1,700° C. When finely divided it has great power 
of occluding or absorbing hydrogen. It frequently pos- 
sesses the power of catalysis. This has already been seen 
in several instances. It may likewise be shown by hold- 
ing a spiral of platinum wire in the neck of a flask of 
strong ammonium hydroxide, slightly warmed. If the 
wire is heated before being thrust into the neck of the 
flask at some point where the ammonia and air are 
mixed, the wire will become red hot and so continue as long 
as the current of ammonia is escaping. The wire may 
even be withdrawn from the flask and reinserted when 
it will again heat up as before. 

4. Uses of Platinum. — On account of its high melting 
point and resistance to attack by acids, platinum is em- 
ployed extensively in the laboratory in the form of cru- 
cibles, wire and foil. In late years, unfortunately for 
science, it has been used very largely in jewelry. Cata- 
lytically, it is used in making sulphuric acid by the 
contact process (p. 261) as well as in other manufactur- 
ing processes. In dentistry platinum wire is used as 
' 'posts" in fastening artificial teeth to the plate. It is 
also used in electric lamps as the connection between the 
inside filament and the outside copper wire. This is 
for the reason that platinum has practically the same 
rate of expansion when heated as glass: any metal used 



436 APPLIED CHEMISTRY 

thus which expands more than glass when heated by 
the current would crack the lamp. 

5. The Other Metals of the Group. — Osmium is re- 
markable for its high melting point, being over 2,000° 
C. Iridium is harder than platinum and is sometimes 
alloyed with the latter for the purpose of securing a 
metal with extreme resistance to acids. It is also some- 
times used on the tips of fountain pens. Palladium is 
of special interest because of its remarkable power of 
absorbing hydrogen and other gases. When heated it 
will occlude about seven hundred times its own volume 
of hydrogen. It does not belong with the platinum met- 
als, but is the most important metal of another special 
group, much lighter in weight, 

Exercises for Review 

1. Name the metals of the platinum group and give atomic 
weights. 

2. Why can these three not be regarded as forming a periodic 
group ? 

3. What can you say of the occurrence of the metals of this 
group ? 

4. Give the important characteristics of platinum. 

5. What precaution must be taken regarding heating low-melt- 
ing metals in a platinum vessel? 

6. What other substances also injure platinum seriously? 

7. In what way have you seen platinum used in chemical experi- 
ments? .Why is it used frequently in the chemical laboratory? 

8. Name some other valuable uses for platinum in the arts.. 

9. Why should platinum not be used for jewelry? 

10. Give some one point of interest about osmium, iridium and 
palladium. Give some use for iridium. 

11. Where does palladium belong in the table? What other 
metals are associated with it? 



TABLES FOR REFERENCE AND GLOSSARY 



438 APPLIED CHEMISTRY 

Solubilities of Common Compounds 

It may be desirable to know at times whether a com- 
pound is soluble in water. A few general rules may be 
helpful and are given below. 

(a) All salts of the sodium group, including those of 
ammonium are soluble, with the exception of two or 
three very uncommon ones. 

(b) All bromides are soluble except those of lead, 
mercury, and silver. 

(c) All carbonates of the sodium group, including 
ammonium, are soluble; all others are insoluble. 

(d) All chlorates are soluble. 

(e) All chlorides are soluble except lead chloride, mer- 
curous chloride, and silver chloride. 

(f) The hydroxides of the sodium group, ammonium, 
and the calcium group are soluble, calcium only moder- 
ately so, Avhile all others are insoluble. 

(g) All nitrates are soluble. 

(h) The oxides of the sodium and calcium group are 
chemically soluble in water, that is, they react to form 
a new compound, the hydroxide. All other oxides are 
insoluble in water. 

(i) Phosphates are insoluble except those of the al- 
kali metals and ammonium. 

(j) Silicates are insoluble except those of the alka- 
lies and ammonium. Even then if mixed with silicates 
of heavier metals they are insoluble. 

(k) The sulphates of barium, calcium, lead and stron- 
tium are insoluble ; others are soluble. 



TABLES FOR REFERENCE 439 



Some Interesting Temperatures 



Absolute zero 


-273° C 


Hydrogen melts 


-260 


Hydrogen boils 


-252.6 


Nitrogen melts 


-214 


Nitrogen boils 


-194 


Oxygen boils 


-182.5 


Alcohol freezes 


-130 


Mercury freezes 


- 39.5 


Water freezes 





Boom temperature 


21 


Ether boils 


34.6 


Human body 


37 


Wood's Metal melts 


60 


Alcohol boils 


78.5 


Water boils 


100 


Sulphur melts (rhomb) 


114.5 


Tin melts 


232 


Lead melts 


327 


Mercury boils 


357 


Zinc melts 


419 


Dull red heat 


650 


Aluminum melts 


660 


Bright red heat 


1,000 


Gold melts 


1,064 


White heat 


1,350 


Iron melts 


1,520 


Platinum melts 


1,750 


Corundum melts 


2,000 (about) 


Oxyhydrogen flame 


2,500 


Oxyacetylene flame 


2,700 


Tungsten melts 


3,000 


Thermit gives 


3,500 (about) 


Electric arc 


4,000 (about) 



440 APPLIED CHEMISTRY 

Tables of Weights and Measures 

Weights 
10 milligrams (mg.) = 1 centigram (eg.) 
10 centigrams = 1 decigram (clg.) 

10 decigrams = 1 gram (g.) 

1,000 grams =1 kilogram (kg.) 

English Equivalents 
1 kilogram — 2.2016 pounds 

28.35 grams = 1 ounce 

1 gram = 15.13 grains 

500 grams = 1.1023 pounds 

The unit of weight in the Metric System is the gram. 

Volumes 
1,000 cubic centimeters (c.c.) — 1 liter 
1 cubic decimeter (c.d.) =1 liter 
1 liter (1.) :=1.056 liquid quarts 

The unit in the Metric System is the liter. 

Length 
10 millimeters (mm.) -1 centimeter (cm.) 
10 centimeters = 1 decimeter (dm.) 

10 decimeters = 1 meter (m.) 

English Equivalents 
1 centimeter = 0.3937 inches 

2.51 centimeters = 1.0 inch 

1 meter — 39.37 inches 

Thermometer Equivalents 
For scientific work the centigrade thermometer is always used 
and readings given in scientific books are always centigrade unless 
otherwise specified. Freezing water is 0° C. and boiling point is 
100° C. 

Centigrade is 32 Fahrenheit and 273 Absolute 
100 " " 212 " " 373 " 

One degree Centigrade = % of a degree Fahrenheit 
One degree Fahrenheit =% of a degree Centigrade 
One degree Centigrade =. One degree Absolute 
To convert centigrade degrees into Fahrenheit, multiply by % 
and add 32, algebraically. This means that if the centigrade read- 
ing is below zero, it Avould have the minus sign and one would be 



TABLES FOR REFERENCE 



441 



substracted from the other. To convert Fahrenheit readings into 
centigrade multiply by % after substracting 32 from the Fahrenheit 
reading. 

List of Elements, Their Symbols and Atomic Weights. (0=16.) 
(The more important elements are printed in heavy type.) 



NAME OF 
ELEMENT 



Aluminum . . . 
Antimony 

Argon 

Arsenic 

Barium 

Bismuth 

Boron 

Bromine 

Cadmium .... 

Caesium 

Calcium 

Carbon 

Cerium 

Chlorine 

Chromium . . . 

Cobalt 

Columbium . . . 

Copper 

Dysprosium . . 

Erbium 

Europium. . . . 

Fluorine 

Gadolinium. . 

Gallium 

Germanium . . 
Glucinum. . . . 

Gold 

Helium 

Holmium. 
Hydrogen 

Indium 

Iodine 

Iridium 

Iron , 

Krypton 

Lanthanum. . 

Lead 

Lithium 

Lutecium .... 
Magnesium. . 
Manganese . . . 
Mercury 



SYM- 
BOL 
~. Al~ 

Sb 

A 

As 

Ba 

Bi 

B 

Br 

Cd 

Cs 

Ca 

G 

Ce 

CI 

Cr 

Co 

Cb 

Cu 

i>y 

Er 

Eu 

F 

Gd 

Ga 

Ge 

Gl 

Au 

He 

Ho 

H 

In 

I 

Ir 

Fe 

Kr 

La 

Pb 

Li 

Lu 

Mg 

Mn 



ATOMIC 
WEIGHT 



27.1 

120.2 
39.88 
74.96 

137.37 

208.0 
11.0 
79.92 

112.4 

132.81 
40.07 
12.00 

140.25 
35.46 
52.0 
58.97 
93.5 
63.57 

162.5 

167.7 

152.0 
19.0 

157.3 

69.9 

72.5 

9.1 

197.2 
3.99 

163.5 
1.008 

114.8 

126.92 

193.1 
55.84 
82.92 

139.0 

207.1 
6.94 

174.0 
24.32 
54.93 

200.6 



NAME OF 
ELEMENT 



Molybdenum. . 
Neodymium. . . 

Neon 

Nickel 

Niton 

Nitrogen 

Osmium 

Oxygen 

Palladium 
Phosphorus . . . 

Platinum 

Potassium .... 
Praseodymium 

Radium 

Rhodium 

Rubidium 

Ruthenium 

Samarium 

Scandium 

Selenium 

Silicon 

Silver 

Sodium 

Strontium 

Sulphur 

Tantalum 

Tellurium 

Terbium 

Thallium 

Thorium 

Thulium 

Tin 

Titanium 

Tungsten 

Uranium 

Vanadium 

Xenon 

Ytterbium .... 

Yttrium 

Zinc 

Zirconium .... 



SYM- 
BOL 

"Mo 
Nd 
Ne 
Ni 
Nt 
N 
Os 
O 
Pd 
P 
Pt 
K 
Pr 
Ra 
Rh 
Rb 
Ru 
Sa 
Ss 
Se 
Si 
Ag 
Na 
Sr 
S 

Ta 
Te 
Tb 
Tl 
Th 
Tm 
Sn 
Ti 
W 

u 

V 

Ne 

Yb 

Yt 

Zn 

Zr 



ATOMIC 
WEIGHT 



96.0 

144.3 
20.2 
58.68 
222.4 

14.01 
190.9 

16.00 
106.7 

31.04 
195.2 
39.1 
140.6 
226.4 
102.9 

85.45 

101.7 

150.4 

44.1 

79.2 

28.3 

107.88 

23.00 

87.63 

32.07 

181.5 

127.5 

159.2 

204.0 

232.4 

168.5 

119.0 

48.1 

184.0 

238.5 

51.0 

130.2 

172.0 

89.0 

65.37 

90.6 



-442 APPLIED CHEMISTRY 

Names and Formulas of the More Common Chemicals 

Acetic acid HC 2 H 3 2 

Alcohol C,H 5 OH 

Alum, ammonium (XH 4 ),A1 2 (S0 4 ) 4 

Alum, potassium K,A1 2 (S0 4 ) 4 

Aluminum oxide A1.,0 3 

Aluminum sulphate A1.,(S0 4 ) 3 

Ammonium bicarbonate XH 4 HCO s 

1 ' carbonate (NH 4 ),C0 3 

' ' chloride XH 4 C1 

hydroxide XH 4 0H 

1 ' nitrate XH 4 X0 3 

' ' sulphate (XH 4 ) 2 S0 4 

Antimony oxychloride SbOCl 

■' ' trichloride SbCL 

{ ' trisulphide Sb 2 S a 

Arsenic trioxide As 2 3 

Barium carbonate BaC0 3 

' ' chloride BaCl 2 

' ' dioxide Ba0 2 

< ' hydroxide Ba(OH) 2 

' ' nitrate Ba(X0 3 ) , 

" oxide BaO 

' ' sulphate BaS0 4 

Bismuth chloride BiCL 

nitrate Bi(X0 3 ) 3 

' • subnitrate BiOX0 3 

' ' trioxide . Bi 2 3 

Bleaching powder GaCl(OCl) 

Borax Xa 2 B 4 0. 

Calcium carbide CaC 2 

1 ' carbonate CaC0 3 

chloride CaCl 2 

1 ' fluoride CaF 2 

hydroxide Ca f OH). 

' ' oxide (lime) CaO 

' ' phosphate Ca 3 fP0 4 ) 2 

sulphate CaS0 4 

Carbolic acid C 6 H 3 OH 

Carbon disulphide CS 2 



TABLES FOR REFERENCE 443 

Chloroform CHC1 3 

Chrome yellow PbCr0 4 

Cinnabar HgS 

Copper acetate Cu(C 2 H 3 2 ), 

' < chloride CuCl, 

" nitrate Cu(N0 3 ) 2 

' ' oxide CuO 

' ' sulphate CuS0 4 

' ' sulphide CuS 

Ether, sulphuric (C 2 H 5 ) 2 

Ferric chloride Fe 2 Cl 6 

"" hydroxide Fe 2 (OH) 6 

' ' nitrate Fe 2 (N0 3 ) 6 

' ' oxide Fe 2 3 

Ferrous sulphate FeS0 4 

Ferrous sulphide FeS 

Fluor spar CaF 2 

Gold trichloride AuCl 3 

Hydrochloric acid HC1 

Hydrofluoric acid HF 

Hydrogen peroxide H,0 2 

Hydrogen sulphide H 2 S 

Hypochlorous acid HCIO 

Iodic acid HI0 3 

Iodoform . CHI 3 

Lead acetate Pb(C 2 H 3 0,) 2 

' ' carbonate PbC0 3 

' ' chloride PbCl 2 

' ' chromate PbCr0 4 

' ' nitrate Pb(N0 3 ) 2 

' ' oxide (litharge) PbO 

' ' sulphate PbS0 4 

Lime CaO 

Litharge PbO 

Lithium chloride LiCl 

Magnesia MgO 

Magnesium carbonate MgCO„ 

1 ' chloride MgCl., 

' ' oxide MgO 

' ' sulphate MgS0 4 

Manganese dioxide MnO, 



444 APPLIED CHEMISTRY 

Mercuric chloride HgCE 

" iodide Hgl, 

" nitrate ..Hg N0 3 ), 

' * oxide Hg 

" sulphide HgS 

Mereurous chloride H?;CL 

iodide Hg I 

" - nitrate Hg, XO 

Minium I 

Phosphine . PE 

Phosphorus pentoxide P,0. 

Plaster of Paris CaSO^O 

Platinum tetrachloride PtCl 4 

Potassium acetate KC.ILO. 

" bicarbonate KHGO s 

" bromide KBr 

" carbonate K.CO 

" chlorate KCIO, 

chloride KC1 

chromate K C i 

" cyanide ETX 

" dichromate KE'r 0. 

• " ferrieyanide K _"-:- GN 

" ferroeyanide KFr CN , 

" hydroxide KOH 

" iodide KI 

" nitrate KNO a 

nitrite KNO, 

" permanganate KMn0 4 

' ' sulphate KJ3Q, 

' ' sulphocyanate KSCX 

Silica SiO, 

Silver bromide AgBi 

" chloride Agd 

" iodide Agl 

nitrate AgKTl 

Sodium acetate XaCJELO, 

" arseniate X: A ~ 

" arsenite NaAs 

" bicarbonate XaHCO. 

" carbonate Na^CO, 



TABLES FOR REFERENCE 445 

Sodium chloride JNTaCl 

' ' hydroxide NaOH 

' ' iodide Nal 

' ' nitrate NaN0 3 

' ' nitrite NaN0 2 

' ' phosphate Na 2 HP0 4 

sulphate Na 2 S0 4 

sulphide .Na 2 S 

sulphite Na 2 S0 3 

thiosulphate Na 2 S 2 3 

Stannic chloride SnCl 4 

' ' oxide Sn0 2 

Stannous chloride SnCl 2 

Strontium nitrate Sr(N0 3 ) 2 

Sulphur dioxide SO, 

Sulphuric acid H 2 S0 4 

Sulphurous acid H 2 S0 3 

Sulphur trioxide S0 3 

Zinc chloride ZnCl 2 

' ' oxide ZnO 

1 ' sulphate ZnS0 4 



GLOSSARY 
Chemical Terms 

Actinic. Actinic light rays are those which have the power of 
producing chemical change in substances, as upon a photo- 
graphic plate. 

Alkali. A soluble hydroxide, with caustic properties, sharp bit- 
ing taste, and power of corroding the skin. 

Allotropic. Literally, another form of an element ; more often 
applied to the unusual form. Ozone as related to oxygen. 

Alloy. A mixture of two or more metals, melted together so as 
to be homogeneous. Example, brass. 

Amalgam. An alloy, one component of which is mercury. 

Amorphous. Without special form; uncrystallized. 

Anesthetic. A substance used to produce unconsciousness. 

Anhydride. An acidic oxide. An oxide forming an acid on the 
addition of water. 

Anhydrous. Without water. 

Antiseptic. An antiseptic is a substance used to prevent decay 
or destroy pathogenic bacteria. 

Basic. Having the properties of a base or alkali. 

Binary. A compound consisting of two elements. 

Calcine. To heat strongly. 

Commercial. A term applied to chemicals not pure but suffi- 
ciently so for all ordinary uses. 

C. P. Chemically pure. Applied to a better grade of chemicals 
than those marked "commercial." 

Decant. To pour off a liquid from a precipitate. 

Deliquesce. To gather moisture from the air and become liquid. 

Desiccator. A vessel used for drying substances. 

Destructive Distillation. Heating a substance in a closed re- 
tort so as to decompose it and produce new substances; as 
in distilling coal. 

Downward Displacement. Collecting a gas heavier than air by 
letting it flow dowmcard into a bottle full of air, thus dis- 
placing the air. 

Distillate. The liquid obtained by distillation. 

446 



GLOSSARY 447 

Dyad. An element with valence of two. 

Effloresce. To give up water of combination at room temper- 
ature and become a powder. 

Electrode. The terminal of a battery. 

Empirical. Applied to a formula which shows composition only. 
Not structural. 

Escharotic. A caustic. A substance which corrodes. 

Filtrate. The liquid which passes through a filter. 

Flocculent. Flaky; often applied to certain precipitates. 

Flux. A substance used to lower the melting point of some sub- 
stance: often it is a solvent for the substance. 

Fractional Distillation. Boiling a liquid and separating it into 
portions or fractions by means of their difference in boiling 
points. 

Gelatinous. Jelly-like or starch-like paste; applied to precipi- 
tates. 

Germicide. A substance destructive of germs. 

Gravimetric. Applied to determining the proportion by iveiglit. 

Halogens. Literally, salt producers; the chlorine family. 

Hydrated. Containing water. 

Hydroxyl. The group HO, found in all hydroxides. 

Hygroscopic. Having the property of becoming moist in damp 
air. 

Indicator. A substance, like litmus paper, used to determine 
when a reaction has been completed. 

Ion. An electrically charged atom or group of atoms. They 
may be either positive, called cations; or negative, called aniotis. 

Isomeric. Two compounds are isomeric when they have the 
same percentage composition, the same empirical formula, 
but are entirely different in properties. 

Monad. An element with a valence of one. 

Monobasic. Applied to an acid having only one displaceable 
atom of hydrogen in a molecule, as hydrochloric acid. 

Mordant. Something used to set the color or dye in cloth. 

Nascent. Literally, being set free; applied to a gas as it is be- 
ing set free from some compound; in the atomic form and 
very active, chemically. 

Neutral. Neither acid nor alkaline in character. 

Neutralization. The process of combining an acid and a base so 
as to exactly destroy the properties of each and form a new 
compound. 



448 APPLIED CHEMISTRY 

Nitrogenous. Containing nitrogen. 

Occlude. To condense within the pores of a metal; as hydrogen 
in platinum or carbon monoxide in hot cast iron. 

Oxidation. The combining of a substance with oxygen. In a 
broader sense, raising the valence of an element. 

Oxidizing Agent. A substance which will bring about oxidation. 
Usually a substance containing oxygen, with which it will 
part readily. Often chlorine or bromine. 

Paste. A very pure form of flint glass used in making imitation 
diamonds. 

Pneumatic. Term applied to the trough used in collecting gases. 

Polymer. A term applied to one compound the multiple of an- 
other. Thus, C 6 H C is a polymer of C 2 H,. 

Precipitate. A solid thrown out in a solution; it may be a 
mere cloud or so very dense and heavy as to settle very 
rapidly. 

Radical. A group of atoms which act chemically as if a single 
element. 

Reaction. The chemical change taking place between two or 
more substances. 

Reagent. A substance used in a chemical reaction. 

Roast. To heat strongly in presence of air; hence to oxidize. 

Saturated. Fully satisfied. Containing all possible. 

Slag. A nearly black glass formed in blast furnaces in the re- 
duction of iron and other metals. 

Sublimate. The substance obtained by sublimation. 

Sublimation. The process of vaporizing a solid which boils with- 
out melting, and collecting the vapors. 

Supernatant. Overlying. Said of a liquid above a precipitate 
which has settled. 

Ternary. Composed of three elements or more. 

Upward Displacement. Method of collecting light gases by let- 
ting them flow upward into a bottle of air, displacing the 
air. 

Volatile. A term applied to substances which readily change in- 
to gas. 

Volumetric. Estimation of quantity by measuring the volume, 
not weight. 



GLOSSARY 449 

Common or Commercial Names 

Agate. A species of quartz, often beautifully colored in con- 
centric rings. 

Alabaster. A beautiful white or delicately tinted form of gyp- 
sum. 

Alum. A double sulphate, containing a univalent and a triva- 
lent metal. Common alum is potassium aluminum sulphate. 

Alumina. Aluminum oxide. 

Amethyst. A variety of quartz, pale violet in color. 

Antichlor. A substance employed to neutralize the chlorine used 
in bleaching. It is generally sodium thiosulphate. 

Arsenic. The usual commercial name for arsenic trioxide. 

Arsenous Acid. A term often applied to arsenic trioxide. Strict- 
ly speaking arsenous acid is H 3 As0 3 . 

Arsine. Hydrogen arsenide also called arseniuretted hydrogen, 
H 3 As. 

Baryta. Barium oxide, BaO. 

Baryta Water. Barium hydroxide, Ba(HO) 2 . 

Bauxite. Hydrated aluminum oxide, A1 2 3 :H 2 0. 

Benzene. More properly called benzol, C 6 H 6 , obtained from 
coal tar. 

Benzine. A light oil resembling ordinary gasoline, obtained from 
petroleum. 

Bicarbonate of Soda. Cooking soda, NaHC0 3 . 

Bituminous. Containing bitumen or oil. 

Blanc de fard. Bismuth oxynitrate, BiON0 3 . 

Blue Vitriol. Copper sulphate crystals. 

Borax. Sodium tetraborate. 

Butter of Antimony. Antimony chloride, so called from its yel- 
low color. 

Calcite. Crystallized calcium carbonate, being three in scale of 
hardness. 

Calomel. Mercurous chloride, Hg 2 Cl 2 . 

Carborundum. Silicon carbide, SiC,used as an abrasive. 

Caustic Potash. Potassium hydroxide. 

Caustic Soda. Sodium hydroxide. 

Chalcedony. A variety of quartz. 

Chalk. A soft, natural form of calcium carbonate. 

Chloride of Lime. Commercial name for bleaching powder. 

Chrome Alum. A double sulphate of potassium and chromium. 



450 APPLIED CHEMISTRY 

Chrome Yellow. Lead chromate, PbCr0 4 . 

Copperas. Ferrous sulphate, green vitriol. 

Corrosive Sublimate. Mercuric chloride, HgCl 2 . 

Corundum. Xative, uncrystallized aluminum oxide, nine in scale 

of hardness. 
Emerald. Aluminum oxide, crystallized, green in color. 
Emery. An impure, native form of aluminum oxide. 
Epsom Salts. Crystallized magnesium sulphate. 
Felspar. A complicated silicate rock, which, decomposed, forms 

clay. 
Fool's Gold. Iron pyrites, FeS,. 
Fuller's Earth. A white variety of clay. 
Green Vitriol. Ferrous sulphate. 
Gypsum. Xative calcium sulphate, CaS0 4 :2H 2 0. 
Hartshorn. An old name for ammonia, so called because made 

from the horns of deer. 
Hypo. Sodium thiosulphate, used in photography as fixing bath 

and as an antichlor. 
Iceland Spar. A transparent, crystallized variety of calcium 

carbonate. 
Jeweler's Rouge. Ferric oxide, native, used in polishing and as 

a paint. 
Kelp. A variety of seaweed. Also applied to the ashes derived 

by burning the seaweed. 
Labarraque's Solution. Sodium hypochlorite, XaClO. 
Lac Sulphuris. A fine white precipitate of sulphur in limewater. 
Laughing Gas. Nitrous oxide X,0. 
Lime. Calcium oxide. 

Limestone. Xative calcium carbonate, uncrystallized. 
Limewater. Calcium hydroxide solution. 
Lunar Caustic. Silver nitrate in stick form containing small 

percentage of silver chloride. 
Magnesia. Magnesium oxide. 
Marble. Crystallized limestone. 
Milk of Lime. Calcium hydroxide solution containing lime in 

suspension. 
Minium. Red Lead, Pb 3 4 . 

Naphtha. A low boiling gasoline obtained from petroleum. 
Nitre. Potassium nitrate. 

Nordhausen's Acid. Fuming sulphuric, H 2 S 2 7 . 
Oil of Vitriol. Sulphuric acid. 



GLOSSARY 451 

Opal. A variety of silica. 

Paris Green. Copper aceto-arsenite. 

Pearl Ash. Pure potassium carbonate. 

Plaster of Paris. Monohydrated calcium sulphate, CaS0 4 :H 2 0. 

Plastic Sulphur. Amorphous sulphur, prepared by pouring boil- 
ing sulphur into cold water. 

Potash. Commercial potassium carbonate. 

Powder of Algaroth. Impure antimony oxychloride. 

Purple of Cassius. A purplish colored compound obtained by 
adding to a solution of gold chloride a small amount of 
stannous and stannic chloride. 

Pyrites. Usually means iron pyrites, FeS 2 . There is also a copper 
pyrites. 

Quicklime. Lime. 

Red Precipitate. Mercuric Oxide. 

Sal Ammoniac. Ammonium chloride. 

Sal Soda. Crystallized sodium carbonate. 

Salt Cake. Sodium sulphate as obtained in the Leblanc proc- 
ess of making sal soda. 

Saltpeter. Potassium nitrate. 

Scheele's Green. Acid copper arsenite, CuHAs0 3 . 

Silica. Silicon dioxide. 

Slaked Lime. Calcium hydroxide, formed by adding water to 
lime. 

Smoky Quartz. A variety of quartz; silica, brown in color, some- 
times almost black. 

Soda. Usually cooking soda is meant. Sodium bicarbonate, 
NaHC0 3 . 

Subnitrate Bismuth. Bismuth oxynitrate, often sold as " bis- 
muth.' ' BiONCv 

Sugar of Lead. Lead acetate, Pb(C 2 H 3 2 ) 2 :3H 2 0. 

Vermilion. Artificial mercuric sulphide. 

White Arsenic. Arsenic trioxide. 

White Lead. Basic lead carbonate; a common white pigment. 

White Vitriol. Crystallized zinc sulphate. ZnS0 4 :7H 2 0. 

Zinc White. Zinc oxide, ZnO. A common white pigment. 



INDEX 



Absolute zero, 85 
Acetylene, 183, 200 

welding, 185 
Acids, 137 

nomenclature of, 139 

organic, 208 

strong and weak, 246 
After-damp, 171 
Agate, 294 
Air, a mixture, 73 

composition of, 73 

early ideas of, 72 

liquid, 80 

pressure of, 89 

value of constituents, 75 
Alabastine, 337 
Alcohols, 206 

denatured, 207 

methyl, 207 

wood, 207 
Aldehydes, 209 
Alkali earths, 336 
Alkali metals, 305 
Alkalies, 138 
Allotrope, 58 
Alum, 399 

Aluminates, 395, 400 
Aluminum, abundance, 392 

alloys of, 398 

bronze, 398 

characteristics, 394 

hydroxide, 399 

preparation, 393 

uses, 395 
Amines, 230 
Ammonia, 147 

characteristics of, 148 

commercial supply, 147 

uses of, 148 
Amylene, 217 
Anhydride, 137 



Anode, 29 
Antichlor, 263 
Antimony, 286 

chloride, 287 

sulphide, 288 

uses, of, 148 
Aqueous tension, 91 

table of, 92 
Argon, 81 
Arsenic, 282 

oxides, 284 

poisoning by, 285 
Arsine, 282 
Asbestos, 380 
Aspirin, 187 
Atomic weights, 99 
Atoms, 97 

number in molecule, 101 

theory of, 97, 99 
Avogadro 's hypothesis, 100 
Azurite, 364 



Babbitt metal, 287 
Baking powders, 328 

alum, 329 

healthfulness of, 331 

phosphate, 329 

tartrate, 329 
Ballistite, 156 
Barium, 343, 344 
Barometer, aneroid, 88 

mercurial, 89 
Bases, 138 

nomenclature of, 138 

strong and weak, 246 
Basic Lining Process, 426 
Bauxite, 394 
Beet sugar, 221 
Benzine, 166 
Biscuits, beaten, 334 



4.-,: 



454 



INDEX 



Bismuth, 288 

compounds, 290 
Black damp, 171 
Blast furnace, 420 
Blast lamp, 195 
Blau gas, 185 

Blow pipe, oxyhydrogen, 195 
Blue prints, 373 
Blue stone, 366 
Blue vitriol, 366 
Bohemian glass, 299 
Bone black, 167 
Borax, 320 
Boyle, Robert, 25 
Boyle's Law, 87 
Bread, aerated, 334 
Brittani, 287 
Bromine, 129 

characteristics, 130 

preparation of, 129 

uses, 131 
Bronze, 404 
Bunsen burner, 194 

application of, 194 
Butane, 204 
Butylene, 217 
Butyrin, 213 



Cadmeia, 24 
Calcium, 336 

characteristics, 337 
chloride, 342 
light, 68, 201 
Candles, 197 
Cane sugar, 220 
Carbohydrates, 219 
Carbolic acid, 187 
Carbona, 175 

Carbon dioxide, characteristics 
of, 172 
cycle, 78 
in air, 78, 171 
preparation, 171 
test for, 175 
uses, 173 
Carbon, forms of, 160 

occurrence, 159 
Carbon monoxide, 168 
characteristics, 170 



Carbon tetrachloride, 355 
Carborundum, 176 
Castner Process, 307 
Catalysis, 52 
Cathode, 29 
Cations, 242 
Celluloid, 156 
Celulose, 222, 226 
Cement, 340 

hydraulic, 341 

natural, 340 

Portland, 340 
Chalcedony, 294 
Chalk, 337, 342 
Charcoal, 166 
Charles' Law, 85, 86 
Chemical changes, 30 
Chemical union, 26 
Chile saltpeter, 306 
Chlorination process, 375 
Chlorine, characteristics of, 
122, 123 

discovery of, 120 

preparation, 120, 121 

uses, 124 
Chrome steel, 428 
Chromium, 411 

characteristics, 411 

compounds, 412 

preparation, 411 

uses, 411 
Cider, hard, 209 
Cleaning, dry methods, 355 
Coal, 163 

varieties, 164 
Cobalt, 419, 432 

barometer, 432 
Coke, 168 
Collodion, 156 

Combustion, definition of, 56, 
190 

old theory, 69 

problems in, 114 

spontaneous, 56 
Compounds, binary, 14 

definition of, 26 

general plan of naming, 27 

percentage composition, 114 

organic, 160, 203 

ternary, 181 



INDEX 



455 



Compounds — C'ont 'd — 

unsaturated, 179 
Concrete, 341 

Conductivity of solutions, 239 
Converter, 425 
Copper, characteristics, 364 

electrolytic, 367 

occurrence, 363 

uses, 365 
Copper acetate, 368 

chloride, 368 

oxides, 368 

sulphate, 368 
Copperas, 429 
Coquina, 336 
Cordite, 156 
Corpuscles, 99 
Corpuscular theory, 99 
Corrosive sublimate, 389 
Corundum, 393 
Cracking oils, 166 
Crisco, 219 
Crown glass, 299 
Cryolite, 393 
C. T. S., 399 
Cyanide process, 375 



Deliquescence, 43 
Dewar bulbs, 81 
Dextrine, 222 
Diads, 179 
Diamonds, 161 

artificial, 162 

composition of, 161 

origin, 161 

uses, 162 
Diastase, 207 
Diffusion of gases, 14, 96 
Disaceharids, 219, 220 
Dissociation, 240 

by solution, 241 
Distillation, fractional, 165 
Dog tooth spar, 337 
Double decomposition, 31 
Drummond Light, 68, 201 
Dutch cleanser, 295 



E 



Efflorescence, 41 

Egg preserving, 297 

Electrolytes, 239 

Electromotive series, 65 

Electrons, 99 

Electrotypes, 366 

Elements, classification of, 265 

definition of, 25 

most abundant, 26 

number, 25 

union of, 28 
Emeralds, 393 
Emulsions, 353 
Enzymes, 224 
Equations, 109 

uses of, 112 
Esters, 212 
Ethane, 204 
Ether, ethyl, 210 
Ethereal salts, 212 
Ethyl butyrate, 212 
Ethylene, 217 



Fats, as foods, 227 

composition of, 216 
Feldspar, 295 
Ferric compounds, 429 
Ferrous ammonium sulphate, 

429 
Ferrous sulphate, 429 
Fertilizers, 281 
Fiber silk, 156 
Firedamp, 204 

Fire extinguisher, Babcock, 174 
Flame, 189 
Flame, candle, 193 

chemical action in, 190 

structure of, 191 
Flash point, 198 
Flint, 294 
Flint glass, 300 
Foods, kinds of, 224 

mineral, 230 

tables, 228, 229, 231, 232 
Fools' gold, 420 
Formaldehyde, 209 



456 



INDEX 



Formic acid, 208 
Formulas, 107 

determination of, 116 

structural, 108 
Freezing point lowering', 235, 

236 
Fulminating mercury, 154 



G 



Galvanized iron, 384 
Gangue, 422 
Ganister, 425 
Gas carbon, 168 

coal, 186 

laws, 85, 87 

illuminating, 199 

liquor, 148 

natural, 166, 183 

pressures, cause of, 97 
problems in, 89, 90 

water, 187 

weight of liter of, 115 
Gasoline, 165, 205 
German silver, 384 
Glass, annealing of, 303 
Glass manufacture of, 300, 301, 

302 
Glucose, 219 
Gluten, 327 
Glycerine, 213, 318 
Glycerol, 213 
Glyceryl esters, 213 
Glycogen, 225 
Gold, characteristics of, 376 

leaf, 376 

mining, 374 

occurrence, 374 
Gram molecule, 104 
Granite ware, 432 
Graphite, 160, 163 
Grids, 408 
Grits, 341 
Green vitriol, 429 
Gunpowder, 153 
Gypsum, 337 



TI 



Halogens, 119 



Hardness, degrees of, 351 

effect on soap, 350 
Hartshorn, 147 
Helium, 82 
Hematite, 420 
Hexane, 204 
Hoffmann apparatus, 37 
Hydrates, 40 
Hydrocarbons, 203 
Hydrochloric acid, 126 

characteristics of, 127 

uses, 127 
Hydrofluoric acid, 128 
Hydrogen, characteristics of, 
67 

discovery of, 63 

occurrence, 63 

preparation from acids, 66 

preparation from oils, 66 

preparation from water, 64 

uses, 68, 69 
Hydrogen chloride, 125 

peroxide, 48 

phosphide, 279 

sulphide, 254 
Hydrogenation, 218 
Hydrolysis, 299, 313 
Hydroquinone, 187 
Hydrosulphuric acid, 254 
Hydroxides, 138 
Hygroscopic substances, 43 
Hypo, 263, 372 



Ice manufacture, 149 
Infusorial earth, 275 
Ink stains, 355 
Inversion, 224 
Iodine, 131 

characteristics, 132, 133 

preparation, 132 

uses, 134 
Ions, 242 

Ions and valence, 243 
Iridium, 436 
Iron, characteristics, 428 

compounds of, 429 

oxidation and reduction of, 
430 



INDEX 



457 



Iron — Cont 'd 
occurrence, 420 
passive state, 428 
pig, 422 

reduction of, 420 
wrought, 424 
Iron carbide, 427 
Iron carbonate, 420 
Isinglass, 295 
Isomorphous, 399 
Ivory black, 167 
Ivy poisoning, 407 



Jasper, 294 



K 



Kaolin, 295 
Kerosene, 165, 205 
Kieselguhr, 154 
Kindling temperature, 57 



Lakes, 400 

Lamp, carbon, 199 

kerosene, 197 

safety, 205 

tungsten, 201 
Lampblack, 469 
Lard, artificial, 216 

compound, 216 
Lavoisier, 69 

Laws, attraction and repulsion, 
29 

Boyle's, 87 

Charles', 85, 86 

definite proportions, 40 

Gay-Lussac's, 103 

Henry's, 173 

multiple proportions, 49 
Lead, characteristics, 405 

family, 402 

occurrence, 405 

uses, 406 
Lead acetate, 406 

carbonate, 407 

chloride, 408 

chromate, 408 

nitrate, 408 



Lead — Cont 'd 

oxides, 406 

pencils, 163 

sulphate, 408 
Leavening agents, 327 
Lighting, electric methods, 199, 
201 

primitive methods, 197 
Lime, 337 

uses, 338, 339 
Limonite, 420 
Litharge, 406 
Lubricating oil, 165 
Lye, 316 



M 



Magnalium, 381, 398 
Magnesium, characteristics, 380" 

compounds, 380 

family, 379 

uses, 381 

oxide, 381 

sulphate, 382 
Magnetic oxide, 420 
Malachite, 364 
Manganates, 417 
Manganese, 416 

oxides, 416 

salts, 417 

steel, 428 
Manometer, 42 
Marble, 337 
Marsh's test, 284 
Matches, 278 
Matter, definition of, 25 

kinds of, 25 

present theory of, 25 

states of, 84 
Mazola, 214 
Meerschaum, 380 
Mercuric chloride, 389 

oxide, 388 

sulphide, 389 
Mercurous chloride, 388 
Mercury, characteristics, 386 

occurrence, 386 

uses, 387 
Metals, cleaning of, 357 
Metathesis, 31 



43 S 



IXDEX 



Meteorites. 420 
Methane, 204 

derivatives of, 206 
Methvlated spirits, 207 

Mica.' 295. 392 
Minium. 406 
Mixtures, 31 
Moisture in air. 79 
Molar weight, 104 
Molecular theory, 95 

weights, 100 

determination of. 103 
Molecules, definition of, 95 

motion of, 96 
Molybdenum. 411 
Monads. 178 
Monosaccharids, 219 
Mordants, 384 
Mucilage,' 222 

N 

Naphtha, 166 

Nascent condition. 283 
Negative, photographic. 371 
Xeutralization, 139 
Niekel, 419 

ammonium sulphate. 431 

characteristics, 431 

compounds, 432 

steel, 428 
Nitric acid, 151. 152, 153 
Xitrocellulose. 155 
Nitrogen, characteristics of. 14' 

compounds. 291 

cycle. 77 

family, 275 

occurrence. 145 

preparation, 146 

value of. 76 
Xitrogen-fixing bacteria, 77 
Nitrogen oxides, 150 
Xitroglycerine, 151 
Xitrous oxide, 150, 151 
Xoble metals, 363 
Xonelectrolytes. 239 

O 

Ochre, yellow. 431 
Oils, as' foods, 227 
Olefins, 217 



Olein, 213 
Oleomargarine. 211 
Onyx. 294 
Oxidation, 56 
Oxides, acidic. 137 

basic. 137 

definition of. 136 
Oxygen, abundance of, 51 

characteristics of. 54. 55 

discovery. 51 

preparation. 52, 53 

uses, 55 
Ozone, characteristics, 60 

preparation, 58 

uses, 60 



Paint, removal of, 356 

Palladium. 434 

Papers, photographic, 372 

Paraffin, 165 

Paris green. 286 

Pectin. 226 

Pentads. 179 

Pentane, 204 

Periodic system, 266 

Periodic Table, 268 

Permanent hardness, 346. 349 

Permanganates, 417 

Permutit system, 349 

Petrified forests, 295 

wood. 291 
Petroleum, 164 

by-products. 165 

kinds of, 165 
Petroleum ether, 165 
Pewter, 287 
Phenol.' 187 
Phlogiston, 69 
Phosphates, 281 
Phosphine. 279 

P h o s p horus. characteristics, 
276, 277 

discovery, 275 

forms of, 276 

preparation, 275 

uses. 277 
Phosphorus oxides, 280 
Picric acid, 157 



INDEX 



459 



Pig iron, 422 
Pintsch gas, 185 
Plaster, land, 340 
Plaster of paris, 239 
Platinum, 434, 435 
Polishing metals, 359 
Polysaccharids, 219 
Potassium, 321 
Potassium bromide, 324 

carbonate, 322 

chlorate, 324 

cyanide, 325 

ferricyanate, 431 

ferrocyanate, 430 

hydroxide, 323 

iodide, 324 

nitrate, 323 
Potash, 322 

Powders, smokeless, 156 
Prestolite, 184 
Propane, 204 
Propylene, 217 
Proteins, 227 
Ptomains, 230 
Pumice stone, 295 
Pyrene, 175 



■Quartz, 295 



Q 



E 



Radicals, 108 
Reactions, additive, 30 
completed, 244, 246 
Red lead, 406 
Rhigoline, 166 
Rock oil, 164 
Pose's metal, 289 
Eouge, 431 
Ruby, 393 

S 

Salivation, 389 
Saltpeter, 324 
Saltrising bread, 333 
Salts, acid, 141 
binary, 142 



Salts— Cont'd 

classes, 140 

definition, 140 

nomenclature, 141 
Sandstone, 294 
Saponification, 318 
Sapphire, 393 
Scale, boiler, 347 
Siderite, 420 

Siemens-Martin Process, 426 
Sienna, burnt, 431 

raw, 431 
Silica, 296 
Silicic acid, 296 
Silicon, 294 

dioxide, 296 
Silver, characteristics, 368 

occurrence, 368 

sterling, 369 
Silver bromide, 370 

chloride, 370 

nitrate, 369 
Simple decomposition, 30 
Slag, 422 
Smalt, 432 
Soap, 317 

cleansing, by, 354 

fillers, 319 
Soda, cooking, 311, 327 
Soda water, 173 
Sodium, characteristics, 308, 
309, 310, 311 

family, 305 
Sodium bicarbonate, 311 

carbonate, 312, 316 

chloride, 306 

hydroxide, 316, 317 

nitrate, 320 
Solder, 414 
Solution, characteristics of, 234 

concentration of, 234 

definition, 233 
Solute, 233 
Solvay process, 311 
Solvent, 233 
Spiegel, 426 
Stamp mill, 376 
Starch, 219, 221 
Stearin, 213 



460 



IXDEX 



Steel. 424 

Bessemer, 425 

:" St, 425 

cementation process. 424 

characteristics. 427 

kinds of. 42 S 

open hearth process. 426 
_. -i:7 
Stibine. 2S7 
Storage battery, 403 
Strontium. 343 
Sugar, beet. 221 

cane. 220 

invert. 224 

of lead. 406 
Suint. 323 
Sulphur, characteristics, 251 

•dioxide. 225 

occurrence, 249 

preparation, 250 

trioxide. 259 

uses. 253 
Sulphuric acid. 259 

characteristics. 2»"2 
manufacture of. 259, 261 
uses, 263 
Sulphurous acid. 259 
Superphosphate, 281 
Symbols. 106 
Sympathetic ink. 432 
Synthetic stones. 393 



Tar. 1S6 

Tartar emetic, 23? 

Temporary hardness. £46, 548 

Tetrads. 179 

Thermit, 397 

Thio sulphuric acid. 263 

Thomas- Gilchrist process, ^-^ 

Tin. alloys. 404 

characteristics. 403 

occurrence. 403 

oxides. 405 

plate. 403 

nses, 403 
T. X. T.. 157 
Transmutation of metals. 24 



Triads. 179 
Tungsten. 411. 414 
Tuyeres, 422 
Type metal, 2S7 



TTnivalence. 173 
Umber, burnt. 431 

raw, 431 
Uranium. 411, 414 



Valence, 173 

in ternary compounds, 131 

variation of, 179 
Vapor pressure lowering. 235 
Vaseline. 165 
Venetian red. 431 
Ventilation. 76 
Vermilion. 339 
Vulcanite,' 253 

TV 

Waste pipes, cleaning of, 357 
Water, alga? in. 46 

characteristics of, 34 

composition of. 37 

forms of. 34 

glass. 297 

hardness in. 346 

in foods. 35 

in human body. 35 

of combination, 40 

of crystallization, 41 

purification of, 45 

supplies. 44 

synthesis of. 39 

vapor in air. 79 

vapor in closed space. 91 

value of. 36 
Welsbaeh mantel. 200 
Wesson oil. 219 ' 
White arsenic. 235 
White lead. 407 
White metals. 334 
Wood's metal. 239 



INDEX 



461 



Zeolyte process, 349 
Zinc, characteristics, 383 
occurrence, 382 
reduction of, 382 



Zinc — Cont 'd 

uses, 384 
Zincates, 386 
Zinc chloride, 385 

sulphate, 384 



snsodaa jjionraaa 



spog 




